Turn the following sentences into the active voice

----- Nội dung dịch tự động từ ảnh -----
II. Turn the following sentences into the active voice.
1. These exercises were done well.
AC
2. This dress must be washed in cold water.
3. No mistakes have been made in his composition.
4. His painting will be exhibited for the first time by New Arts gallery.
5. This house was built 100 years ago.
6. These artificial flowers are made of silk.
7. The lessons are being written by the students now.
8. This job has to be done at once.
9. These animals at the zoo are fed twice a day.
10. The operation is going to be performed by French doctors.
11. All the arrangements have been made.
12. When was this radio manufactured?
13. They couldn't be found anywhere.
14. Is mathematics taught in this school?
15. Fortunately the machinery wasn't damaged by the accident.