Modal verbs are used to indicate certainty, possibility or probability of an event.

Do you know when to use can, could or should? Test your knowledge with these exercises.

Choose the best option to complete the sentences below. 

1. I _________________ fall asleep last night. ( can’t / mustn’t / couldn’t )

2. An alligator _________________ kill a person with just one bite. ( may / can / must )

3. You __________ take my umbrella. I think it _________________ rain later. ( can / might / should )

4. We _________________ boil the lake water before we can drink it. ( may / can / must )

5. People _________________ take care of nature. ( may / can / should )

6. You _________________ be at two places at once. ( wouldn’t / mustn’t / can’t )

7. We _________________ cross the street when the light is red. ( may / can / can’t )

8. People ________________ live on the Moon. ( may / mustn’t / can’t )

9. We _________________ show our vacation photos to her, she’d be too jealous. ( must / shouldn’t / can’t )

10. You _________________ reach the shelf, it is too tall. ( must / can / can’t ) 

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