题目内容：

If you become rich,you will have a difficult time knowing ( ) your real friends are.
A that B who C which

优质解答

你要看后面的从句中缺少什么成分,“your real friends are.”可见有主语your real friends,有系动词are,没有表语,这个表语可以是形容词可以是名词,所以在三个选项中B最适合.