By the time he was twelve he ______ a chemistry lab of his own.　 A. built 　 B. has built  C. had built 　 D. was building

Last term our maths teacher set so difficult an examination problem _____ none of us worked out.

　 A. that 　 B. as    C. so that 　 D. which

Mr. and Mrs. Scott prefer a restaurant in a small town to ________ in so large a city as New York.

A. this　                  B. one　          C. it               D. that

The man and the horse _____ fell into the river were drowned.

　 A. Which 　 B. who  C. that 　 D. of which

I’ll never forget the holiday ______ we spent together.

　 A. When 　 B. how   C. in which 　 D. that