Ответ:

Форма have to обозначает необходимость, а don’t have to — отсутствие необходимости.

  1. 2a) I have to do homework every evening.
    2b) I don’t have to do English homework every evening.
  2. 3a) My sister has to tidy her room on Saturdays.
    3b) My sister doesn’t have to go shopping with my parents.
  3. 4a) We have to do Maths tests every week.
    4b) We don’t have to go to school in the holidays.

Ответ: 2a have to; 2b don’t have to; 3a has to; 3b doesn’t have to; 4a have to; 4b don’t have to.