1.This is an old computer which\that works much slower.
2.They stayed with me for three weeks during which time they drunk all the wine I had.
3.The picture(that)we are looking at was drawn by a fifteen-year-old student.
4.The picture at which we are looking was drawn by a fifteen-year-old student.
5.I have many students to whom I am going to send postcards.
6.You’re the only one whose advice he might listen to.
7.I’d like a room whose window looks out over the sea.
8.The explorer took only such men and things as he really needed into the jungle.
9.Such people as have made great contributions to the world should be greatly respected.
10.Let’s meet at the same place as we did yesterday.
11.Shakespeare is a famous writer,as everyone knows.
12.As everyone knows,Shakespeare is a famous writer.
13.Shakespeare,as everyone knows,is a famous writer.
14.Potato can be grown in places where(in which)it’s too cold to grow rice.
15.I shall never forget the days when（on which）we worked on the farm.
16.Can you tell me the reason why(for which)the car broke down.
17.The reason that the car broke down caused the accident.
18.He told me the way(that\in which)he solved the problem.
19.He told me how to solve the problem.
20.I have been to the places(that\where\in which)the Indians live.