题目内容：

Don't use words,expression or phrases____only to people with specific knowledge.
A.being known B.having been known
c.to be known D.known
这个题目的C和D选项怎么区分啊?
关于动词-ed 形式作定语 应该怎么区分?
那A和B选项呢？该怎么区分？