20．The reason ______ he didn't come was _____he had to take care of his sick mother.

A. why; that　　　 B. why; which　 　　C. which; why　 　D. that; for

19．_______ we need more practice is quite clear.

A. When　　　　　 B. What　　　 C. That　　　　 D. 不填

18．It was with great joy ______ he received the news _____ his lost son would soon return home.

A. because; that　　 B. that; that　　 C. because; which　　 D. that; 不填

17．A well-written composition ______ good choice of words and clear organiza­tion among other things.

　　　 A. calls on 　　　　　　　 B. calls for　　　　　　　 C. calls up　　　　　　　 D. calls in

16．　　 warmly for his work, he was too　　　 to fall asleep.

　　　 A. Praising;　 excited　　　　 　　B. To praise;　 exciting

C. Praised;　 exciting 　　　　　　　　　　　 D. Praised;　 excited