问题补充:
If he keeps on working so hard, he will sooner or later.
A. break off
B. break up
C. break out
D. break down
答案:
A. break off
B. break up
C. break out
(答案→)D. break down
解析:考查动词短语辨析。A折断;B关系破裂,分解;C(战争,火灾)爆发;D机器出故障,身体垮掉;句意:如果他继续如此努力地工作,迟早会垮掉。根据句意说明D正确,