—Can you work out the problem?—I can’t your explain how to do it.A. but forB. exceptC. apa

问题补充：

—Can you work out the problem?—I can’t your explain how to do it.

A. but for

B. except

C. apart from

D. unless

答案：

A. but for

B. except

C. apart from

(答案→)D. unless

解析：连词辨析。A. 要不是 B.除了；要不是 C.除了；缺少 D.除非。句意：你能算出这道题吗？——我不能除非你能解释一下怎样做。选D。