Why didn't you remind him of the possible danger?But what ____ otherwise?He never listens to me．A．could I do B．could I have done C．should I do D．must I have done

Why didn't you remind him of the possible danger?
But what ____ otherwise?He never listens to me．
A．could I do B．could I have done C．should I do D．must I have done

otherwise,此句使用虚拟语气.
对现在的虚拟：would + do；
对过去的虚拟：would + have done.
--Why did you leave without a word of warning to John?
为什么你不教训一下约翰就走了?
--But what could I have done otherwise?He never likes to listen to me.
不然我还能做什么呢?他从来都不听我的.

A