ответ:
1. yesterday i had to answer all these letters. 2. do we have to write a dictation today? — yes, tomorrow we begin a new lesson. 3. shall i invite anna to dinner? — yes, please. 4. did you have to stay home because the weather was bad? 5. you definitely must come and have a look at our son.— with pleasure. 6. shall i go for a walk with nick now? - no, you don't have to.
you know that he has to go to bed at three o'clock. 7. i don't like to stay up late, but sometimes i have to. 8. i'm glad i didn't have to finish this work yesterday. 9. you should visit your friend. yesterday he did not come to class. 10. why didn't you come? — i couldn't, i had to take my children to the doctor. 11. you don't need to go to the library, we have got a lot of books at home, and you may take any book you like. 12. he shouldn't wake us so early.
is
Это 3-е лицо и используют форму глагола to be - is