he asked nothing because he was able to understand what they had talked about.He asked nothing because he was able to understand what they had talked about.A.must B.was able to C.can D.may

he asked nothing because he was able to understand what they had talked about.He asked nothing because he was able to understand what they had talked about.A.must B.was able to C.can D.may
he asked nothing because he was able to understand what they had talked about.
He asked nothing because he was able to understand what they had talked about.
A.must B.was able to C.can D.may

he asked nothing because he was able to understand what they had talked about.He asked nothing because he was able to understand what they had talked about.A.must B.was able to C.can D.may
be able to 是能够做某事,must是必须,
这里是过去时态,所以不能用can和may
结合语境应该是选B

他什么都没问，因为他能明白他们谈论的东西。

他没有问任何问题因为他可以听懂他们讨论的东西

B，be able to 意思是可以，有能力、、
此句译为：他什么也没问，因为他能够知道他们谈论的事情

1。表示成功地做了某事时，只能用was/were able to， 不能用could。但是答案只有can 没有could 更不对了
2。因为must只用于肯定句，语气很强。2. 若对过去情况的推测用must have加过去分词。
3。may语气表怀疑 不肯定 与原文背景不符