1. He can never COME in time.

2. Fortunately, people could PREVENT this catastrophe.

3. He may GET the first prize.

4. You mustn’t COME home so late.

5. May I HAVE a look at the photo?

6. Did they have TO TURN to a private detective? They didn’t have TO TURN to a private detective.

***7. Fortunately, the police was able TO PREVENT this tragedy.

8. The detective is TO CARRY OUT an investigation.

9. You ought TO BE more decisive.

10. You shouldn’t THINK so much about him.

11. You didn’t need TO GET UP early yesterday, so I had a good sleep.

12. I am independent and I don’t need TO ASK  my parents for money.

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** 7 Fortunately, the police was able TO PREVENT this tragedy.

!!!! Должно быть = the police were able to... = существительное police - всегда множественного числа )))

from: bbc.co.uk

'The police are coming! The police are coming!' Police is a noun which describes a collection of police officers. This means it has no singular form and always uses a plural verb.