I doubt _______ they can complete the bridge ahead of time.

I doubt _______ they can complete the bridge ahead of time.
A、whether
B、that
C、why
D、what
【正确答案】：A
【题目解析】：doubt 用在肯定句中，之后的宾语从句用 whether 或 if 引导。用在否定句中，后接宾语从句用 that 引导。