Distinction between the active voice & the passive voice....

In this exercise I had to identify whether these sentences were written in an active or passive voice. In order to complete the exercise I focused on whether the 'doer' or the 'subject' was the focus of each sentence. I had trouble with a couple though (namely 10 & 13), so I had to make educated guesses.

Please highlight mistakes, I need some clarification! Thanks, Matt.

1. My wife wrote the letter. 1- Active
2. The charge was made by the police. 2- Passive
3. The storm will destroy the harvest. 3- Active
4. John took the dog for a walk. 4- Active
5. The sun was eclipsed by the moon. 5- Passive
6. The man in the black hat found the child. 6- Active
7. This task can be done by small children. 7- Passive
8. My father painted the house. 8- Active
9. This bone has been buried by the dog. 9- Passive
10. It takes a long time to think of these example sentences. 10- Passive
11. The drawings were done by a famous artist. 11- Passive
12. Music is composed by clever people. 12- Passive
13. There was a cup of coffee on the table, but now it’s gone. 13- Active
14. I was born under a wandering star. 14- Active
15. Mark was given one month to write this book. 15- Active
16. In 1999, the moon moved across the sun covering it by 97%. 16- Active