He-----unwisely,but he was at last trying to dosomething helpful.

问题描述:

He-----unwisely,but he was at last trying to dosomething helpful.
A.should act B.would act C.may have acted D.must have acted
参考答案为C,可是后面的was不是表示过去吗,前面应该是had acted 为什么是have,

may have acted 情态动词加完成时态,表对过去的推测 他那时也许做的不明智 was trying过去进行时 something helpful 不定代词形容词做定语后置 整个句子是以but连接的并列句