（ ）we could find no sign of the man and the search had to be terminated.
A、Possibly
B、Sensibly
C、Regrettably
D、Doubtfully
【正确答案】：C
【题目解析】：possibly ad. 可能地Sensibly ad. 明智地，得体地Regrettably ad.遗憾地Doubtfully ad.可疑地e.g. He decided, very sensibly, not to drive when he was so tired.他很累，所以决定不开车，这是很明智的。
