otherwise否则,此句使用虚拟语气.
对过去的虚拟：would + have done.本句就用could have done
翻译一下就是：
--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.
“史上巨难解释”一个高中英语单选题----无数人回答过,但都解释的不好.