If he keeps on working so hard he will sooner or later.A. break offB. break upC. break ou

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，