Ответ:
1) Negative:The pupils had not translated the text before the bell rang
Interrogative: Had the pupils translated the text before the bell rang?
2) Kate hadn't done her lessons by eight o'clock.
Had Kate done her lessons by eight o'clock?
3)Peter hadn't studied English before he entered the institute.
Had Peter studied English before he entered the institute?
4)The girls hadn't cleaned the room by the time their mother came back.
Had the girls cleaned the room by the time their mother came back?
5)We hadn't reached the village before the sun set.
Had you reached the village before the sun set?