15. You ... not come to help them tomorrow: the work is done. 16. You ... not change the whole text as the
beginning is all right. You ... only rewrite the second part of it. 17. Ann ... not go
to his birthday party yesterday because she ... go to the dentist. 18. You ... take
medicine three times a day before meals. 19. She ... decorate a room nicely.
15. May
16. Can, must
17. Could, had to
18. Must
19. Is able to
Объяснение: