Английский язык

Нужно написать к каждому предложению объяснение почему там такой ответ.

1. Carol and Michael have known each other since they were three years old. (know)

2. Has Gemma borrowed any books from the library? (Gemma / borrow)

3 I'm really hungry because I haven`t had any breakfast. (not have)

4. Have you downloaded that new song from the Internet? (you / download)

5 We have bought a new computer. (buy)

6 The postman hasn`t delivered any letters today because it's Sunday. (not delivered)

7 The children have finished their homework, so they can go out and play. (finish)

8 Don't worry. You aren't late. The film hasn`t started(not start)