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I/
1. History is taught by Miss Hien Trang.
2. The letter will be delivered by John.
3. The telephone was invented by Bell.
4. The photo was taken by my brother.
5. The new hospital will be opened by them.
6. The report was written by Mr.Brown yesterday.
7. The streets are cleaned by them every day.
8. Our house is painted every four years.
9. The glass pieces are dried completely.
10. Trees and flowers will be planted in the school garden.
II/
2. It is simple to use the computer.
3. It's difficult to learn Spanish.
4. It is important to keep the environment clean.
5. It is difficult to get a good job.
III/
2. I was very happy that I got good grades this semester.
3. He is delighted that he knows the answer.
4. We were surprised that we saw you in town.
5. They were very happy that they passed the entrance examination.
6. Yourr parents were very disappointed that you didn't pass the English exam.