You have a difficult time knowing who your real friends are.
4个回答

个人认为,“knowing who your real friends are”这个由“knowing”引导的现在分词短语在句子中作“a difficult time”的定语,实际上,也就是作“a difficult time”这个名词短语的中心词“time”的后置定语.

另外,“knowing”在这里是现在分词,后面跟着“who”引导的宾语从句作宾语.