7-20 предложения !!! помогите пожалуйста past simple и past perfect !!!

1 Tom returned from the cinema at five o'clock
2 Tom had returned from the cinema by five o'clock
3 I finished my homework at seven o'clock
4 I had finished my homework by seven o'clock
5 He thought that he had lost the money
6 Ann told me that she had seen an interesting film
7 When I came home mother had already cooked dinner
8 When father returned from work, we had already done our homework
9 When the teacher entered the classroom, the pupils had already opened their books
10 Kate gave me the book which she had bought the day before
11 Nick showed the teacher the picture which he had drawn
12 The boy gave the goats the grass wich he had brought from the field
13 Mother saw that Nick hadn't washed his hands
14 The teacher understood that Lena hadn't done her homework
15 I knew that my friend hadn't come yet
16 When I woke up yesterday, father had already gone to work
17 Nick though that his father hadn't come yet
18 Mary told us that she had cooked a good dinner
19 Yesterday I found the book which I had lost in summer
20 When we came to the station, the train had already left