مدونة التربية و التعليم في الجزائر – دروس، فروض، نتائج امتحانات مدونة التربية والتعليم في الجزائر | تحضير الدروس، فروض واختبارات، نتائج البكالوريا وBEM، مسابقات التوظيف، والتوجيه المدرسي للطلاب وأولياء الأمور.
Modal Verbs for Deduction: Must, Can’t, May, Might, Could
Learning Objectives:
- Understand how to use modal verbs for logical deduction
- Distinguish between certainty, probability, and possibility
- Use must and can’t for strong deductions
- Use may, might, and could for weaker probability
Introduction:
Modal verbs of deduction are used to make logical guesses about situations. We use them when we are not 100% sure, but we have evidence or reasons to believe something.
Degrees of Certainty:
| Modal Verb | Degree of Certainty | Example |
|---|---|---|
| Must | Very certain (95-99%) | He has a key. He must be the owner. |
| Can’t / Couldn’t | Very certain it’s impossible (95-99%) | She was in Paris. She can’t be here now. |
| May | Possible (50%) | It may rain later. Take an umbrella. |
| Might | Less possible (30-40%) | He might come to the party. |
| Could | Possible (30-40%) | That could be true. |
1. MUST (deduction that something is true)
We use “must” when we are almost certain something is true because of evidence.
- He’s been working all day. He must be tired. (evidence: working all day)
- The lights are on. They must be at home.
- She passed the exam. She must have studied hard. (past: must + have + past participle)
2. CAN’T / COULDN’T (deduction that something is impossible)
We use “can’t” (or “couldn’t”) when we are almost certain something is NOT true.
- He can’t be at work. It’s midnight.
- She speaks English fluently. She can’t be a beginner.
- They can’t have finished the project already. (past)
3. MAY, MIGHT, COULD (possibility)
We use these modals to say that something is possible but not certain.
- May: More formal, slightly more certain than might.
- Might: Less certain, more tentative.
- Could: Similar to might, often used in suggestions.
Examples:
- Take an umbrella. It may rain later.
- He isn’t answering. He might be sleeping.
- That could be the postman at the door.
- She may have left already. (past possibility)
Present and Past Forms:
| Tense | Form | Example |
|---|---|---|
| Present | modal + be / verb | He must be at home. / He must work hard. |
| Present Continuous | modal + be + verb-ing | She might be sleeping. |
| Past | modal + have + past participle | They must have arrived. |
| Past Continuous | modal + have + been + verb-ing | He could have been waiting. |
BAC-Style Exercises:
Exercise 1: Choose the correct modal
1. John passed his driving test. He (must be / can’t be) very happy.
2. It’s freezing outside. It (must be / might be) 40 degrees Celsius.
3. She hasn’t eaten all day. She (must be / can’t be) hungry.
Answers:
1. He must be very happy.
2. It can’t be 40 degrees Celsius.
3. She must be hungry.
Exercise 2: Rewrite using a modal of deduction
1. I’m sure he is a doctor. (He looks like one) – He ______ a doctor.
2. I’m sure she isn’t 30 years old. (She looks younger) – She ______ 30 years old.
3. Perhaps they will arrive late. (Traffic is bad) – They ______ late.
Answers:
1. He must be a doctor.
2. She can’t be 30 years old.
3. They may/might/could arrive late.
Exercise 3 (BAC Style): Complete the sentences
1. A: Someone is knocking at the door. B: It ______ (be) the postman.
2. A: Ali got 20/20 in the exam. B: He ______ (study) very hard.
Answers:
1. It could be the postman.
2. He must have studied very hard.
Summary:
Use MUST when you are almost sure something is true. Use CAN’T when you are almost sure something is not true. Use MAY, MIGHT, or COULD when something is possible. For the past, add “have + past participle”.
