the jurors reached an agreement on the criminal case.There____any doubt about it.

the jurors reached an agreement on the criminal case.There____any doubt about it.

解题思路：四个选项都是情态动词加完成时，表对过去的推测

据题意，陪审员对于本案意见一致，言下之意，一定不会有什么疑问，所以用肯定性的推测

而C选项，即使要用也是用would,因为是对过去的推测
A选项，是，本不应该有疑问，言下之意，还是有疑问
B选项，是，也许有疑问追问还是没明白C为什么不行啊，would的否定式不是won't么，另外can't have done意为本不能还是本不必？追答would 的否定形式是wouldn't,加完成时含有虚拟的成分,语气没有can have done强

can't have done就是表达一定不会，肯定不会，语气类似于must have done，可是又没有mustn't have done的用法