11. I should have bought that car.
 If only I had bought that car.
12. There was never any answer when we rang.
 Every time we rang, there was never any answer.
13. Carol has no difficulty in making friends.
 Carol finds making friends easy.
14. He does it as if he was a fool.
 He did it like a fool.
15. Carol is a vegetarian. I cooked the meal for her last week. She enjoyed it.
 Carol, who is a vegetarian, enjoyed the meal I cooked for her last week.
16. I bought a new typewriter. It cost me a lot of money.
 The new typewriter which I bought cost me a lot of money.
17. What a funny story!
 It is a funny story.
18. She and I have never been there before.
 Neither she nor I have been there before.
19. You took those photographs, so we were arrested.
 If you hadn't taken those photographs, so we wouldn't have been arrested.
20. The professor is excellent. I am taking her course.
  The professor whose course I am taking is excellent.
21. Although his leg was broken, he managed to get out of the car.
 In spite of his broken leg, he managed to get out of the car.
22. It may rain on your way home, so take a raincoat with you.
 In case It may rain on your way home, take a raincoat with you.
23. Unless someone has a key, we can’t get into the house.
We can only get into the house if someone has a key.
24. That question cannot be answered satisfactorily.
 There is no satisfactory answer to that question.
25.Alan worked too hard at exam time, and this led to his illness.
 Alan’s illness was caused by his working too hard at exam time.

11. If only I had bought that car.

12. Every time we rang, there was no answer.

13. Carol finds it not difficult to make friends.

14. He does it like a fool.

15.Carol, who is a vegetarian, enjoyed the meal I cooked for her last week.

16. The new typewriter which I bought cost me a lot of money.

17. It is a funny story.

18. Neither she nor i have been there before.

19. If you didn't take those photo , we weren't arrested.

20. The professor whose course I am taking is excellent.

21. Inspite of his broken legs, he managed to get out of the car .

22. in case it rains on your way home, take a raincoat with you

23. We can only get into the house if someone has a key.

24. There is no satisfactory answer to that question 

25. Alan's illness resulted from his working too hard at the office