Complete the sentences using must, mustn’t, (don’t) have to, couldn’t, ought to, shouldn’t. 1) You … work on Saturday. It’s a day off.
2) I saw Tina in town last night. – You … have seen her. She was on holiday in Spain.
3) If you don’t understand anything you … ask your teacher to help.
4 You … take your dog into the supermarket. It’s not allowed.
5) I can’t go to the cinema with you today. I … visit my grandparents.
6) The exam was rather difficult and I … answer all the questions.
7) You … be at work by nine o’clock. – I promise I won’t be late.
8) I feel very tired today. – You … have stayed so late last night.
9) I’ve got a terrible toothache. – You … visit a doctor.

с английским

1) You don't have to work on Saturday. It’s a day off.
Explanation: "Don't have to" is used to express that something is not necessary or obligatory. In this case, it means that working on Saturday is optional.

2) I saw Tina in town last night. – You couldn't have seen her. She was on holiday in Spain.
Explanation: "Couldn't have" is used to express that it was not possible for something to happen in the past. In this case, it means that it was not possible for the speaker to see Tina because she was on holiday in Spain.

3) If you don’t understand anything, you must ask your teacher to help.
Explanation: "Must" is used to express something that is necessary or required. In this case, it means that it is necessary for the student to ask their teacher for help if they don't understand anything.

4) You mustn't take your dog into the supermarket. It’s not allowed.
Explanation: "Mustn't" is used to express prohibition or something that is not allowed. In this case, it means that it is not allowed to take a dog into the supermarket.

5) I can't go to the cinema with you today. I must visit my grandparents.
Explanation: "Must" is used to express something that is necessary or required. In this case, it means that it is necessary for the speaker to visit their grandparents, so they cannot go to the cinema.

6) The exam was rather difficult and I couldn't answer all the questions.
Explanation: "Couldn't" is used to express that it was not possible for something to happen in the past. In this case, it means that the speaker was not able to answer all the questions on the exam because it was difficult.

7) You ought to be at work by nine o’clock. – I promise I won’t be late.
Explanation: "Ought to" is used to give advice or make suggestions. In this case, it means that it is advisable or expected for the person to be at work by nine o’clock.

8) I feel very tired today. – You shouldn't have stayed so late last night.
Explanation: "Shouldn't have" is used to express regret or that something was a bad idea or decision in the past. In this case, it means that the speaker believes it was a bad idea for the person to have stayed out so late last night because they feel tired now.

9) I’ve got a terrible toothache. – You must visit a doctor.
Explanation: "Must" is used to express something that is necessary or required. In this case, it means that it is necessary for the person with the toothache to visit a doctor.