I asked him whether he had done all the work himself whether he had had any assistance.A.

问题补充：

I asked him whether he had done all the work himself whether he had had any assistance.

A. and

B. but

C. nor

D. or

答案：

A. and

B. but

C. nor

(答案→)D. or

解析：因为只有or才能表示选择，意为“(是…) 还是”。