Modal verbs – permission, obligation, prohibition, necessity

You _______use this product without protection.

• are not meant

• aren't supposed

• 'd better not

Answer explanation

➪ We use had better + infinitive (without to) to talk about actions we think someone should or shouldn’t do. There is often a negative resultif the action is carried out. We normally use the shortened form ‘d better, and the negative form is never contracted: ‘d better not.

You _______ go to the ceremony if you don't feel like it. It'll be very boring anyway.

• haven't to

• don't have to

• mustn't

Answer explanation

The negative forms mustn’t and don’t have to are completely different. Mustn’t is used to express prohibition (an obligation not to do something), whereas don’t have to + infinitive to say that something is not necessary.

We took too much risk. We ______ that decision.

• shouldn't make

• mustn't made

• needn't have made

Answer explanation

When something was not necessary but we did it, we can use both didn’t need to + infinitive and needn’t have + past participle.

He _______ the bus because his brother picked him up at the station.

• didn't need to take

• needn't have taken

• shouldn't have taken

Answer explanation

When something was NOT necessary and we did NOT do it, we use didn’t need to (NOT needn't have done).

He ________ so much money on the trip last summer.

• had better not spend

• shouldn't have spent

• shouldn't spend

Answer explanation

We cannot use shouldn't spend or had better not spend here because we use these forms to talk about the present or future.

We use perfect modal verbs to talk about the past.

The refugees _____ work outside the camp.

• mustn't

• had better not

• are not allowed to

Answer explanation

The only correct form is are not allowed.

We can say mustn't work (NOT mustn't to work), and we can say had better not work (NOT had better not to work).

We couldn't find a hotel so we________in the car. It was so uncomfortable!

• must have slept

• had to sleep

• should have slept

Answer explanation

We need to express past obligation, and had to is the only form we have in this sentence to do it.

We should have slept in the car means 'we didn't sleep in the car but it was the right thing to do'.

We must have slept in the car means 'I'm sure we slept in the car'.

You ________forget to take your medicine.

• ought not

• mustn't

• don't have to

Answer explanation

We use mustn't to express prohibition and don't have to to express lack of necessity.

We can say ought not to forget (NOT ought not forget).

We ________ early because it was a holiday, so we slept till late.

• didn't have to get up

• needn't have got up

• needn't get up

Answer explanation

When something was not necessary but we did it, we can use both didn’t need to + infinitive and needn’t have + past participle.

However, when something was NOT necessary and we did NOT do it, we use didn’t need to (NOT needn’t have done).

You ________ call me as soon as you arrived. I was very worried!

• were meant to

• were supposed

• must

Answer explanation

We can use be supposed/meant to + infinitive to express obligation or permission, to say what we should or shouldn’t do