Речення в Present Perfect і 3-4 запитання до нього

My friend has just finished reading an interesting book.

1) Who has just finished reading an interesting book?

2) Has my friend just finished reading an interesting book?

3) What has my friend just finished reading?

4) Has my friend just finished reading an interesting book or a letter from a friend?

5) What has my friend just done?

6) Whose friend has just finished reading an interesting book?