Ⅱ. 单项填空（共15小题;每小题1分, 满分15分）
21. This little boy is the_____ all the trouble.
A. cause of B. reason of C. cause for D. reason for
【解析】选A。句意：这小孩是一切麻烦的根源。 cause指造成某事发生的原因，the cause of sth. ;reason是指逻辑上的原因，常用the reason for. . . 。
22. Never before______ such a difficult time, and nor_____ .
A. we have experienced; they have
B. have we experienced; have they
C. did we experience; they did
D. we had experienced; had they
【解析】选B。考查时态和倒装。 Never和nor位于句首时，引起句子倒装，排除A项；由never可知应选现在时。故选B。
23. Before we moved into the new house, we bought many_____.
A. furnitures B. furniture
C. pieces of furniture D. pieces of furnitures
【解析】选C。句意：在搬进新房子之前，我们买了许多家具。 furniture为不可数名词。许多家具many pieces of furniture。
