No doubt he knew the news.A. thatB. ifC. whetherD. but

问题补充：

No doubt he knew the news.

A. that

B. if

C. whether

D. but

答案：

(答案→)A. that

B. if

C. whether

D. but

解析：考查doubt的用法。doubt用于肯定句时用whether引导同位语从句；用于否定句时，用that引导。句意：无疑他知道这个消息。根据No可知本句为否定句，句首省略there is，故选A。