Ability
His arm is broken, so he isn’t able to / may not write.
His arm is broken, so he isn’t able to write.
Should / Could I have a piece of cake, please?
Could I have a piece of cake, please?
The doctor says I might / must get more exercise.
The doctor says I must get more exercise.
Tomorrow is a holiday, so we mustn’t / don’t have to get up early.
Tomorrow is a holiday, so we don’t have to get up early.
I'm sure he doesn't know the secret. =
He might / can't know the secret.
He can't know the secret.
He stopped the car so he should / could rest for a while.
He stopped the car so he could rest for a while.
Mom, I finished my chores. Can / Must I go out with my friends now?
Mom, I finished my chores. Can I go out with my friends now?
You look great in brown. You should / can wear it more often.
You look great in brown. You should wear it more often.
She had too much to drink. She mustn't / doesn't have to drive home.
She had too much to drink. She mustn't drive home.
Maybe she is on vacation. =
She might / must be on vacation.
She might be on vacation.
He mustn't / can't reach it. He’s not tall enough.
He can't reach it. He’s not tall enough.
I've finished the book. You may / have to borrow it.
I've finished the book. You may borrow it.
When you are on a diet, you ought to / could drink a lot of water.
When you are on a diet, you ought to drink a lot of water.
The teacher says we could not / cannot use a calculator on our exams.
The teacher says we cannot use a calculator on our exams.
It's possible she has a dog. =
She could / can have a dog.
She could have a dog.
I am able to / could make people laugh when I was young.
I could make people laugh when I was young.
I'm not sure if we can / could park the car here.
I'm not sure if we can park the car here.
You must / may come over for dinner. I won’t accept no for an answer.
You must come over for dinner. I won’t accept no for an answer.
In some countries, women mustn't / might not show their faces in public.
In some countries, women mustn't show their faces in public.
I'm sure David is at home. =
David can / must be at home.
David must be at home.
Lucy couldn't / won't be able to come to the party later. She is at home sick.
Lucy won't be able to come to the party later. She is at home sick.
May / might I help you with your bags?
May I help you with your bags?
You can / had better brush your teeth before you go to sleep.
You had better brush your teeth before you go to sleep.
You can't / couldn't drink alcohol before the age of 21 in the US.
You can't drink alcohol before the age of 21 in the US.
Perhaps you need to restart the computer. =
You must / may need to restart the computer.
You may need to restart the computer.