he stops driving himself like this he'll have a breakdown.A. UntilB. OnceC. SinceD. Unl

问题补充：

he stops driving himself like this, hell have a breakdown.

A. Until

B. Once

C. Since

D. Unless

答案：

A. Until

B. Once

C. Since

(答案→)D. Unless

解析：D 考察连词。句义：如果他在不停止这么卖命的工作，他就会崩溃。Until意为直到..为止；once一旦；since既然，unless除非，如果不..相当于if..not。根据语境可知D正确。