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