Поставьте соответствующую форму глагола to be:
1he...at home last night
2...you ready for the lesson
3i...not late for the lecture
4the students...in the classroom
5... you at the concert yesterday
6i...20 last year
7my friend...not there
8we...policeman before school
9i...at a football match last Saturday
10the sky...blue
11nick and pete...friends at school