Answer:
1. Unkind remarks easily upset my friend.
2. I was told the news this morning by a friend.
3. The little boat was overturned by the huge wave.
4. Much time is spent with Anu's friends.
5. People say that insecticides kill bacteria.
6. The matter shall be discussed tomorrow.
7. They gave a warm welcome to the President.
8. Smoking should have been stopped.
9. The elephant was given the peanuts by the children.
10. An architect is deigning the library.
11. A lot of grain is grown in the south.
12. Sudhir was made manager of the firm.
13. The army built the bridge.
14. When can this project be started by your brother?
15. National parks attract tourists.
16. My question hasn't been answered.
17. They nominated him for the best actor award.
18. The sleeping child has been awaken by her voice.
19. She was said to be a genius.
20. Why was her enemy invited to her party.
21. The man was brought on a charge for theft by the police.
22. Emergency aid is given to the accident victims.
23. They inspected the machines last week.
24. The conference building was badly damaged by the fire.
25. The crash damaged several vehicles.
Explanation:
Basically, when transforming an active sentence into passive voice there are few rules to be remembered.
1. The object of the active sentence becomes the subject of the passive sentence.
2. The verb "to be" is used in the tense of the active sentence.
3. The verb of the active sentence is used in its past participle form and it, with the correct form of the verb "to be", forms the verb of the passive sentence.
Backtracing these steps we can easily convert a passive sentence into its active voice.