一道英语题I've got some wonderful news.We've ……

问题描述:

一道英语题I've got some wonderful news.We've ……
-I've got some wonderful news.We've been invited to the palace ball.
-Really?____
A.I don't believe soB.I can't believe it
答案选B请问为什么,为什么不选A

是应该选B的,首先呢语感上告诉我们B很顺;然后看一下语境:第二个人的语气是很吃惊,所以选B.
A只是普通的陈述,与Really?不相衬.