1 I have five balloons of which three are yellow.
2 David is my friend with whom I often play tennis.
3 He has twenty books of which only two are interesting.
4 Mr Johnson apologised for the mistake which we complained to him.
5 The Antarctic about which men know little is covered with snow and ice all year round.
6 The shop from which we bought the air-conditioner is not far from my house.
7 You'd better tell her the name of the book which she can find information about the project there.
8 They have just started their trip to Tibet for which they prepared for about a month.