【题目】He had to pause from time to time to wipe the sweat from his forehead, because the air—conditioning system ______________.
A. broke in B. broke up
C. broke out D. broke down
在线课程【答案】D
【解析】
试题分析：考查动词短语。句意：他时不时地停下来擦去额头的汗水，因为空调出毛病了。A.break in打断； 闯入； 开始工作；B.break up结束，散开；分解；C.break out爆发；D.break down崩溃，垮掉；根据词义，故选D项。