B1 Focus: These words form the context for this lesson on modal verbs. As you study each term, notice how it appears in the Grammar Lab — you will use these words to practise deduction and speculation.
Grammar Lab: Modal Verbs of Deduction & Possibility
Key concept: In English, when you are not stating a confirmed fact but drawing a conclusion from evidence, you use modal verbs. The modal you choose tells the listener how certain you are. This lab covers six key modals and how they interact with adverbs and continuous forms.
How certain are you?
can't
0%
Logically impossible
could
~25%
Theoretical / specific possibility
might
~35%
Possible (softer)
may
~45%
Real possibility
must
~95%
Almost certain (from evidence)
impossible ←→ almost certain
⚠️ None of these are 100% — that is why they are called modal verbs of deduction, not facts. Only is / are states a known fact.
1. The Logic of Certainty — Must & Can't (95–99%)
must→You are logically convinced it is true (evidence = YES)He has three Ferraris. He must be rich.
can't→You are logically convinced it cannot be true (evidence = NO)She isn't answering the door. She can't be home.
⚠️ You are reasoning from evidence — not reporting a known fact. If someone told you directly, use is, not must.
❌ Fact (confirmed — someone told you) He is rich.
✔ Deduction (you saw the Ferraris and concluded) He must be rich.
📝 Easy: Choose must or can't. Ask yourself: does the evidence point towards it being true (must) or away from it (can't)?
1. Look at all those fresh tracks in the mud. A large animal ___ live near here.
2. She has been studying biology for eight years. She ___ be a complete beginner.
3. That bird sings for six hours every day. It ___ love making noise.
4. The fox hasn't touched the food we left out. It ___ be hungry.
5. He volunteers at the nature reserve every weekend. He ___ care deeply about conservation.
🎯 Hard: Write must be or can't be. Think about the evidence given — does it make the conclusion very likely or logically impossible?
1. The bear has not been seen since October, and it is now January. It ___ hibernating in its den right now.
2. That plant is flowering in December with no water or sunlight. It ___ a real plant — it must be artificial.
3. She identified every bird we saw by its call alone. She ___ an expert ornithologist.
4. He says the wolf is friendly. He ___ serious — wolves are wild predators.
5. These footprints are enormous — much bigger than a fox. This ___ a large predator like a bear or a wolf.
2. The "Maybe" Zone — May, Might & Could (Possibility)
may→Real, medium possibility (~40–50%)She may know the answer.
might→Possible but less certain (~30–40%)It might rain tonight.
could→Cautious / theoretical possibility (~20–35%)That could be a fox track.
💡 In everyday British English, may and might are often interchangeable. Could tends to sound slightly more cautious or tentative.
Modal
Meaning
Example
Certainty
may
maybe / perhaps
The deer may return at dusk.
medium (~40–50%)
might
maybe / perhaps (softer)
It might rain tonight.
medium-low (~30–40%)
could
possible / theoretical
That could be a fox track.
lower (~20–35%)
📝 Easy: All three modals are possible. Choose the one that best fits the certainty hint in brackets.
1. I haven't seen the hedgehog for a while. It ___ be hibernating. (medium possibility)
2. That noise in the bushes ___ be a badger — they are common in this area. (real chance)
3. I'm not sure about tomorrow's weather — it ___ snow at higher altitude. (lower certainty)
4. She ___ know which plants are edible — she studied botany. (medium, real chance)
5. There are rare orchids in these woods — you ___ see one if you're lucky. (unlikely but possible)
🎯 Hard: Fill in the blank with may, might, or could + the correct form of the verb in brackets.
1. Those birds haven't arrived yet. The migration ___ (delay) due to the cold weather.
2. I spotted something moving. It ___ (be) a deer or possibly a wild boar.
3. The wolves ___ (return) to this valley — conditions are improving.
4. That plant ___ (not / survive) the frost — it is a tropical species.
5. She ___ (already / find) the badger's burrow — she left two hours ago.
3. Negative Speculation — Can't vs May Not / Might Not
can't→Logically impossible — the evidence rules it out completelyHe can't be 15. He drives a car.
may not / might not→Maybe not — you are not sure either wayHe may not be at work today. (I don't know.)
⚠️ For present deduction, always use can't — notcouldn't. Couldn't refers to the past or a hypothetical.
✔ Present deduction (logical impossibility) He can't be serious.
✘ Less natural in this meaning He couldn't be serious. ← avoid for present deduction
Form
Meaning
Example
can't
Logically impossible — evidence rules it out
She can't be the owner — she's only 12.
may not
Maybe not — uncertain, still possible either way
He may not be back before dark.
might not
Perhaps not — slightly more uncertain than may not
She might not know about it.
📝 Easy: Choose can't, may not, or might not.
1. That animal ___ be a wolf — wolves haven't lived in this region for 50 years. (logically impossible)
2. She ___ come to the field trip — she mentioned she had a doctor's appointment. (uncertain — maybe not)
3. He ___ be allergic to pollen — he spends every day outdoors with no problems. (logically impossible based on evidence)
4. The swallows ___ arrive until next month — the temperature is still too low. (uncertain prediction)
5. That ___ be the same fox — this one has a completely different marking on its tail. (logically impossible)
🎯 Hard: Write the correct negative modal phrase. Think carefully about the type of negation.
1. He says he has never seen a wolf in the wild. That ___ be true — he has lived next to the forest his whole life. (logically very hard to believe)
2. The rare orchid ___ survive in the city park — it needs very specific soil conditions. (impossible given the conditions)
3. She ___ be interested in the conservation project — she hasn't replied to any of the messages. (uncertain — maybe not)
4. Those birds ___ be migrating right now — it is mid-winter and the whole flock is still here. (logically impossible now)
5. He ___ want to join the night walk — he goes to bed very early. (uncertain — we don't know for sure)
4. Continuous Modals — Guessing What Is Happening Right Now
Formula: modal + be + verb-ing
must be + -ing→Almost certain it is happening right nowShe must be working. (I can see the light on.)
might/may/could be + -ing→Possibly happening right now — less certainThe fox might be hunting.
General habit:She must work hard. → deduction about her usual behaviour
Right now:She must be working hard. → she is doing it at this moment
Must be + -ing (almost certain now)
She hasn't answered. She must be sleeping.
The bear must be hibernating — it's January.
Strong evidence → strong conclusion about now.
Might/May/Could be + -ing (possible now)
The fox might be hunting in the field.
Those birds could be nesting up there.
Less evidence → softer guess about now.
📝 Easy: Complete each sentence with the correct continuous modal form.
1. I can hear the owl. It ___ (must / call) from the oak tree at the edge of the field.
2. Those deer tracks are fresh and lead into the forest. They ___ (might / graze) nearby.
3. She left with her binoculars three hours ago. She ___ (must / watch) birds near the wetland.
4. Those plants look droopy. They ___ (could / not / get) enough water.
5. There is a strange rustling in the bushes. A hedgehog ___ (may / look) for food.
🎯 Hard: The verb in brackets is in the base form. Choose the right modal AND put the verb into the continuous form.
1. The wolf hasn't been seen at the den for two days. It ___ (hunt) in the forest further east. (possible right now — we don't know for sure)
2. I can see lights on in her office at 11 pm. She ___ (work) very late tonight. (almost certain)
3. The bees are extremely active around that flower. They ___ (pollinate) it right now. (almost certain from evidence)
4. The river looks slightly different. It ___ (change) course — this happens slowly over decades. (lower possibility)
5. The bear ___ (not / sleep). Look — the den entrance has fresh claw marks from today. (logically impossible right now)
5. Modal Adverbs — Strengthening or Weakening Your Certainty
definitely→Very strong (100%) — pairs with simple verb: is / willHe is definitely the expert.
probably→Likely (~70–80%) — pairs with is / will / wouldShe is probably tired.
⚠️ Avoid unnatural combinations:
✘ She definitely must be tired. — redundant: both words say the same thing
✘ She must probably be tired. — unnatural word order in British English
✔ Use must alone, or is probably without must.
Adverb
Strength
Natural pairing
Example
definitely
Very strong (100%)
Simple verb (is / will)
He is definitely the expert.
probably
Likely (~70–80%)
is / will / would
She is probably tired.
possibly
Weak (~20–30%)
might / could
He might possibly know.
📝 Easy: Choose the most natural adverb for each sentence.
1. I have no doubt whatsoever — she is ___ the best botanist I have ever met.
2. The wolf will ___ return to the same den next winter — they are very territorial.
3. There is a very small chance that the rare plant survives the frost — it might ___ make it.
4. He has studied predators for twenty years. He is ___ an expert on wolf behaviour.
5. The birds are quite late this year. They will ___ arrive next week.
🎯 Hard: Rewrite using the adverb given. Keep the same meaning. Type the full new sentence.
1. "She must be exhausted after the field trip." → Rewrite using probably (no modal):
2. "He is the most experienced guide in the group." → Add definitely:
3. "She might come to the night observation." → Add possibly to make it even softer:
4. "She definitely must be tired" is unnatural because it repeats the same certainty twice. Write one natural corrected version:
5. "It is probable that it will snow tonight." → Rewrite with probably in a natural position:
6. Can vs Could — General Truth vs Specific Possibility
can→General truth — always or generally possible (a fact about the world)Wolves can travel 50 km in a night.
could→Specific situation — might happen in this particular caseIt could be cold tomorrow.
General (can):Snakes can be dangerous. — true about snakes in general
Specific (could):That snake could be dangerous. — this particular snake, right now
✔ Can — general truth Snakes can be dangerous. (A fact about snakes in general)
✔ Could — specific situation That snake could be dangerous. (This particular snake, right now)
📝 Easy: Choose can or could.
1. Bears ___ run faster than most people think — it is a well-known fact.
2. We ___ see a red squirrel today if we're lucky — they were spotted here yesterday.
3. Living in a dense forest ___ be very isolating — it is a general challenge for rangers.
4. It ___ rain this afternoon — look at those dark clouds building up.
5. Bees ___ travel up to five kilometres from their hive — this is a general biological fact.
🎯 Hard: Write can or could. Decide first whether the sentence states a general truth or a specific situation.
1. Migratory birds ___ cover thousands of kilometres without stopping — it is extraordinary. (general truth about the species)
2. Those clouds over the mountain ___ bring hail — the forecast is uncertain. (this particular situation)
3. In some seasons, the forest floor ___ be completely covered in wildflowers. (general seasonal truth)
4. That rustling in the leaves tonight ___ be a hedgehog or a mouse — I saw both earlier. (this evening, specific)
5. Foxes ___ adapt to almost any environment — urban or rural. (general truth about fox biology)
Passive to Active Voice
B1 Practice: Each sentence is in the passive voice. Rewrite it as an active sentence using the agent in brackets as the subject. Keep the same tense. Type the full active sentence.
📝 Exercise 1 — Present & Past Simple Rewrite as an active sentence. The agent is given in brackets.
1. "The forest is protected by the government." → [The government]
2. "The rare orchid was discovered by a botanist in 2005." → [A botanist]
3. "The wolves are tracked by researchers every season." → [Researchers]
4. "The bird's nest was destroyed by the storm." → [The storm]
5. "The flowers are pollinated by bees every spring." → [Bees]
6. "The wetland was drained by farmers fifty years ago." → [Farmers]
7. "The bear is fed by tourists at the picnic area." → [Tourists]
8. "The new nature reserve was opened by the minister last week." → [The minister]
9. "Seeds are spread by the wind across the meadow." → [The wind]
10. "The predator was spotted by the ranger near the campsite." → [The ranger]
📝 Exercise 2 — Present Perfect & Past Perfect
1. "The habitat has been studied by scientists for decades." → [Scientists]
2. "Three new species had been found by explorers before the survey ended." → [Explorers]
3. "The fox's burrow has been blocked by fallen leaves." → [Fallen leaves]
4. "The ecosystem had been damaged by pollution before the clean-up began." → [Pollution]
5. "The wolf pack has been observed by the research team for two years." → [The research team]
6. "The old tree had been struck by lightning twice." → [Lightning]
7. "Several rare plants have been catalogued by botanists this year." → [Botanists]
8. "The migratory route has been changed by new wind patterns." → [New wind patterns]
9. "The prey had been caught by the predator before we arrived." → [The predator]
10. "The conservation plan has been approved by the committee." → [The committee]
🎯 Exercise 3 — Continuous Tenses
1. "The wolves are currently being monitored by a team of biologists." → [A team of biologists]
2. "The forest floor was being cleared by volunteers when the rain started." → [Volunteers]
3. "The foxes are being tracked by GPS collars." → [GPS collars]
4. "The new habitat is being created by conservation workers this month." → [Conservation workers]
5. "The rare fern was being photographed by the botanist when the deer appeared." → [The botanist]
6. "The animal tracks are being analysed by the research team." → [The research team]
7. "The young birds were being fed by their mother every hour." → [Their mother]
8. "The endangered plants are being grown by horticulturalists in the lab." → [Horticulturalists]
9. "The deer was being stalked by a wolf when we spotted them." → [A wolf]
10. "The wetland is being restored by an environmental charity." → [An environmental charity]
🎯 Exercise 4 — Modal Passive to Active Rewrite as active, keeping the modal.
1. "These wetlands must be protected by the government." → [The government]
2. "The wolf can be tracked by its distinctive footprints." → [Its distinctive footprints]
3. "All visitors should be warned by the rangers about the bear." → [The rangers]
4. "The endangered species might be saved by the new conservation law." → [The new conservation law]
5. "New plants may be introduced by the ecologists to restore the area." → [The ecologists]
6. "The bear could be disturbed by campers if tents are set up here." → [Campers]
7. "Nesting sites must be left undisturbed by hikers during breeding season." → [Hikers]
8. "The fox might be scared away by the noise." → [The noise]
9. "Seeds can be dispersed by birds over huge distances." → [Birds]
10. "The habitats should be connected by wildlife corridors." → [Wildlife corridors]
🎯 Exercise 5 — Mixed Tenses (Passive to Active)
1. "The rare moth has been studied by entomologists since 1998." → [Entomologists]
2. "The deer are being counted by park rangers this morning." → [Park rangers]
3. "The plants were damaged by the frost last night." → [The frost]
4. "The migratory birds had been ringed by researchers before they left." → [Researchers]
5. "The meadow is mowed by the farmers twice a year." → [The farmers]
6. "The nesting area was being surveyed by ornithologists when the storm hit." → [Ornithologists]
7. "The water quality is tested by the environmental agency monthly." → [The environmental agency]
8. "The wolf's territory has been mapped by GPS over five years." → [GPS]
9. "The trees are planted by local schoolchildren every spring." → [Local schoolchildren]
10. "The fox had been caught by the trap before anyone realised." → [The trap]
Cloze Text: A Walk Through the Forest at Dawn
Task: Read the text and select the correct modal word or phrase in each gap. Think carefully about the level of certainty implied by the context.
Key Word Transformation (KWT)
B1 Exam Skill: Rewrite the second sentence so it has the same meaning as the first, using the KEY WORD given. Do not change the key word. Use between 2–5 words.
Exercises
Practice: These exercises consolidate all modal forms from this lesson. Work through each set systematically.
Tense Writing: Plants & Animals in Context
Task: Put the verb in brackets into the correct tense. All tenses are mixed across each exercise. Where more than one tense is grammatically correct, both answers are accepted. Note: Future Perfect Simple and Continuous are not tested in this lesson.
📝 Exercise 1
1. Wolves ___ (hunt) in packs — it is a well-known fact about their behaviour.
2. By the time we arrived, the bear ___ (already / return) to its den.
3. The rare orchid ___ (discover) by a botanist in this meadow in 2012.
4. Look — the fox ___ (dig) a new burrow right now at the edge of the field.
5. The swallows ___ (migrate) to Africa every autumn since I was a child.
6. It ___ (be) very quiet in the forest just before dawn — almost no sound at all.
7. When we checked the camera trap, a large wolf ___ (walk) past it at 3 am.
8. These wetlands ___ (protect) by law since 1998.
9. The researcher ___ (study) the wolf pack for two hours when the rain began.
10. Foxes ___ (be) highly adaptable animals — they thrive in both rural and urban areas.
📝 Exercise 2
1. The bees ___ (pollinate) the flowers in this meadow every summer without fail.
2. Three new species of plant ___ (find) in the valley before the survey team left.
3. The deer ___ (graze) in the clearing when we suddenly spotted the wolf.
4. Scientists ___ (study) the effects of climate change on migratory birds for years.
5. The old oak tree ___ (fall) in the storm last night — it was over 300 years old.
6. Every morning, the blackbird ___ (sing) from the same branch outside my window.
7. The nature reserve ___ (expand) by the charity over the next few years.
8. The plants ___ (not / survive) if you don't water them regularly.
9. A fox ___ (live) near our garden for years — we see it almost every evening.
10. The habitat ___ (destroy) by pollution before any steps were taken to protect it.
🎯 Exercise 3
1. By the time the conservationists arrived, the wolves ___ (already / leave) the area.
2. This species ___ (not / see) in the wild for over twenty years before it was rediscovered.
3. The birds ___ (currently / monitor) by GPS tags fitted by the research team.
4. If you walk quietly, you ___ (probably / see) deer near the stream at sunset.
5. The forest floor ___ (be) covered in bluebells every spring — it is breathtaking.
6. By the time you read this, the bear ___ (return) to its summer territory in the mountains.
7. The fox ___ (dig) the burrow for three hours when we first spotted it.
8. Rare plants ___ (often / damage) by visitors who do not stay on the paths.
9. How long ___ (you / observe) this particular wolf pack before you published your findings?
10. Neither of the two camera traps ___ (capture) a clear image of the animal yet.
🎯 Exercise 4
1. She ___ (photograph) every bird species in this region before she retired.
2. The ecosystem ___ (slowly / recover) since the invasive species was removed.
3. There ___ (be) no confirmed wolf sightings in this region for thirty years.
4. The whole flock ___ (feed) peacefully when the hawk appeared and scattered them.
5. These seeds ___ (not / germinate) unless they are exposed to frost first.
6. The conservation project ___ (run) for five years by the time it receives its first major funding.
7. The wolf's movements ___ (record) on camera every night for the past six months.
8. Both the fox and the badger ___ (use) the same burrow system for years.
9. The insects ___ (pollinate) crops in this area long before modern farming techniques arrived.
10. The ranger ___ (track) the bear for two days when she finally found its den.
🎯 Exercise 5
1. Which species ___ (most / affect) by habitat loss in the past century?
2. The badger ___ (not / seen) near the farm since the fence was built last autumn.
3. Each of the seven nesting sites ___ (check) by rangers before the breeding season began.
4. There ___ (be) a family of foxes living in the garden while we were away last summer.
5. The plant ___ (still / flower) when the first frost came — it had been a very warm autumn.
6. Both the red squirrel and the pine marten ___ (benefit) from the new reforestation scheme.
7. How many species ___ (the scientists / identify) in this valley before they ran out of funding?
8. The wolves ___ (reintroduce) to the national park five years ago, and the ecosystem has changed noticeably since then.
9. Neither the foxes nor the badgers ___ (return) to the area after the fire.
10. The morning light ___ (filter) through the tree canopy when I first heard the wolf howl.