Can, Could, Be Able to

Exercises

Explanation

1. Can — present ability, possibility, permission

A. Ability (skills or physical ability)

Can shows what someone is able to do now.

• I can play the guitar.

• She can speak three languages.

• Can you drive?

B. Possibility (something is possible in general)

• Prices can be very high in this area.

• The weather can change very quickly here.

C. Permission (informal)

• Can I open the window?

• You can borrow my book.

Negative: cannot / can’t

• I can’t find my keys.

• You can’t park here.

Questions:

• Can you help me?

• What can I do for you?

2. Could — past ability, polite requests, possibility

Could is the past form of can, but it also has other uses.

A. Past ability

Used for general ability in the past.

• I could swim when I was five.

• She couldn’t read before school.

B. Polite requests (more polite than “can”)

• Could you open the door, please?

• Could I use your phone?

C. Possibility in the present or future (less certain than “can”)

• We could go to the cinema later.

• It could rain tomorrow.

D. Criticism or disappointment (could + perfect infinitive)

Used when something did not happen, but you think it should have.

• You could have called me earlier!

• They could have helped us, but they didn’t.

Negative: could not / couldn’t

• I couldn’t finish the test in time.

• She couldn’t believe her eyes.

3. Using can and could to express doubt or surprise

Sometimes we use questions with can or could to show that we are unsure or surprised.

Present doubt

• Can that be true?

• Can he be serious?

Past doubt (more uncertain)

• Could she have been right?

• Could he have worked there for so long?

Negative doubt = expressing impossibility

• That can’t be his car.

• She can’t be telling the truth.

• He couldn’t have said that.

• They couldn’t have left so early.

4. Be Able To — ability in all tenses

We use be able to to talk about ability when can cannot be used.

A. Future ability (because “can” has no future form)

• I will be able to join the meeting tomorrow.

• She will be able to drive next year.

B. Past ability in a specific situation

Use was/were able to when someone succeeded in one situation.

• We were able to reach the airport on time.

• He wasn’t able to fix the computer.

C. Present ability (less common than “can”)

• I am able to help you now.

• She is able to solve this problem.

Comparing “can” and “be able to”:

• Can = general ability

• I can ski. (I know how)

• Be able to = ability in a specific moment

• I was able to ski down that difficult slope yesterday.

5. Positive, Negative, and Questions

6. Extra Uses and Expressions

A. Can’t help + -ing = cannot stop yourself

• I can’t help laughing — the joke was so funny.

• She couldn’t help smiling when she heard the news.

B. Can’t possibly = it’s impossible for me

• I can’t possibly finish this today.

• She couldn’t possibly agree to that.

C. Can’t but + verb = have no other choice (formal)

• I can’t but refuse the offer.

• She couldn’t but ask him the question.

7. Examples in Everyday Contexts

Ability

• My sister can draw beautifully.

• He could run very fast when he was a teenager.

Permission

• Can I sit here?

• Could I leave a bit early today?

Possibility

• This road can be dangerous at night.

• It could get cold later.

Requests

• Can you send me the file?

• Could you repeat that, please?

Future ability

• After a few lessons, you will be able to surf.

Quick Summary

• can = present ability, possibility, informal permission

• can’t = impossibility or prohibition

• could = past ability, polite requests, weaker possibility

• could have + V3 = criticism about the past

• be able to = ability in any tense, especially future or specific situations