1 When the teacher entered the classroom, the students had already opened their books.
2 My friend showed me a mobile phone which he had bought the day before.
3 The teacher understood that John hadn't prepared for the exam well enough.
4 We had returned from the cinema by nine o’clock.
5 I had done all my work by six o’clock.
6 She said that she had spent her holiday in Spain.
7 Then he came to the shelf, took one book and began to read it.
8 I had just found the money I was looking for.
9 When did your friend return from the South? – He returned yesterday.
10 They left England when he was a child.
11. You (to see) Peter? – I (not to see) him since last month - тут я считаю не корректный вопрос, так как перфект в настоящем времени нужно использовать, а не в прошедшем, т.е. Have you seen Peter? - I haven't seen him since last month.