Unit 3: Modal Verbs of Deduction and Persuasive Writing

Degrees of certainty

How to read the evidence

• Positive evidence that makes you almost certain → must.
• Evidence against the idea → can't, not mustn't. Mustn't means prohibition, not deduction.
• A possibility you cannot confirm → may / could / might; might is weaker than may in exam keys.
• Sentences from the unit: "The risks can't be completely avoided, but they can be reduced." / "Families should take precautions during storms."

Quick check

1. She … be at home; her lights are off. → can't
2. They … be tired after walking all day in the heat. → must
3. This … be the right place; the map shows we're still far away. → can't

Degrees of certainty in the past

Form

• modal + have + past participle (V3): must have experienced, can't have caused, might have felt.
• Never use the past simple after a modal: must have went is wrong.

Quick check

1. The streets are flooded. There … been a heavy storm last night. → must have
2. They … heard the announcement — they didn't show up. → can't have
3. She … forgotten about the meeting. It's likely. → may / might have

The two forms

• should + base verb → advice about the present or the future: You should eat more vegetables.
• should have + past participle → blame or regret about the past: You should have taken an umbrella.
• shouldn't have + past participle → criticism of a past action: You shouldn't have left the windows open.

Examples from the unit

• Fishermen should have prepared earlier for the changes in the sea.
• Citizens should have listened carefully to awareness campaigns in the past.
• The state should have invested in sea walls many years ago.

Quick check — with answers

1. You look tired. You … (go) to bed earlier. → should go
2. We … (help) him when he asked for support. → should have helped
3. It was raining. You … (take) an umbrella. → should have taken
4. She … (listen) to her teacher more carefully. → should have listened
5. You … (eat) more vegetables. They're good for you. → should eat

The five characteristics

1. Clear opinion or point of view: the writer states their position clearly.
2. Strong reasons and evidence: reasons, facts, examples or statistics support the opinion.
3. Emotional appeal: words that make the reader feel something — fear, hope, guilt or pride.
4. Persuasive language: must, should, need to, important, urgent, we all know, clearly, obviously, and rhetorical questions such as "What will happen if we do nothing?"
5. Call to action: tells the reader what to do after reading.

The article's argument in three moves

• Problem: worldwide issues such as climate change, poverty and hunger seem impossible for one person to affect.
• Claim: these problems can't be ignored and require collective action; small but meaningful steps combine into a huge impact.
• Call to action: reduce waste, support ethical businesses, advocate for fair policies — and recognise that every positive action contributes to a larger solution.

Language to reuse

Essay task

• Write a persuasive essay of 180–200 words on "Small Actions, Big Impact".
• Keep one claim, two reasons with evidence, one emotional appeal, and a final call to action.

A. Complete with a modal of deduction

1. Many people in poor regions … (not cause) climate change, but they suffer the most. → can't have caused
2. That community … (experience) serious flooding after last week's hurricane. → must have experienced
3. Activists … (feel) frustrated when leaders ignore their demands. → may / might feel

B. Choose the correct answer

1. You haven't eaten anything since morning, you … be hungry.   a. must   b. might   c. can't   d. should → a
2. It's very cold outside, but the windows are open. He … have forgotten to close them.   a. must   b. should   c. can't   d. shouldn't → a
3. The alarm didn't go off last night, so it … have been turned off by mistake. I'm sure.   a. must   b. might   c. can't   d. should → a
4. There is no food in the fridge. She … have gone shopping this morning.   a. must   b. might   c. can't   d. may → b
5. The garden looks wet. It … have rained last night.   a. must   b. might   c. can't   d. should → a
6. He … be at home now because his car is not in the driveway.   a. must   b. might   c. can't   d. should → c
7. They … left early because their bags are gone.   a. must have   b. might have   c. can't have   d. should have → a
8. The lights are still on even though everyone left. Someone … forgotten to switch them off.   a. must have   b. might have   c. can't have   d. should have → a

C. Listening task: Climate Change and Coastal Cities

• Why are coastal cities like Alexandria at risk? What do scientists emphasise about sea levels? What problems do families and shop owners face? How can the state protect coastal areas? What can citizens do to help?
• Answer these from the audio track before you look at any transcript — the exam tests detail, not memory of the topic.