have to (in its correct form). Sometimes it is possible to use either; sometimes only have to is possible. Examples: Well, it's 10 o'clock. I must (or have to)... go now. Ann was feeling ill last night. She had to leave the party early. 1 You really......................... work harder if you want to pass that examination. 2 Many children in Britain......................... wear uniform when they go to school. 3 Last night Don suddenly became ill. We........................ call the doctor. 4 Ann has......................... wear glasses since she was eight years old. 5 I'm afraid I can't come tomorrow. I....................... work late. 6 I'm sorry I couldn't come yesterday. I...................... work late. 7 Tom may.......................... go away next week. 8 We couldn't repair the car ourselves. We....................... take it to a garage. 9 When you come to London again, you1....................................... come and see us.

1 You really .have to.. work harder if you want to pass that examination. 2 Many children in Britain..have to... wear uniform when they go to school. 3 Last night Don suddenly became ill. We..had to... call the doctor. 4 Ann has...had to.. wear glasses since she was eight years old. 5 I'm afraid I can't come tomorrow. I..have to... work late. 6 I'm sorry I couldn't come yesterday. I..had to... work late. 7 Tom may..have to... go away next week. 8 We couldn't repair the car ourselves. We..had to.. take it to a garage. 9 When you come to London again, you  must....... come and see us.