怎么解释这道题？？谢谢了！

一个句子只能有一个谓语动词吧……所以A选项排除
C选项格式错误，定语从句中缺少谓语动词，X
B和D的话……个人还是倾向与D…………
D选项含有情不自禁的意思……

can 和be able to 都可以表示能力.can泛指一般的能力,而且只有两种形式,即:can, could．be able to 则主要指具体做到了某件事的能力，其形式主要是靠be 发生变化，所以形式比can 多．可以说：I can swim. I am able to swim. 但是不能说：All the people could escape from the big fire in time. 只能说：All the people were able to escape from the fire in time.

B
be able to 和can 用于过去时态中时，be able to含有成功做成某事的意思，而could没有
如：They was able to escape from the building .他们从这座大厦里逃了出来。

这道题不是两者的区别，而是中间插入状语，选B，同样句子主体为She was too excited，其后为状，所以不应填任何有句子倾向的选项