Don't use words,expressions,or phrases____only to people with specific knowledge.A being knownB having been knownC to be knownD known为什么 还有D是现在完成时的被动语态吗?有人说:其实这个句子写成定语从句,是这样:Dont't use words,expressions,or phrases that are known only to people with specific knowledge.我们可以把that are 省略。为什么that are 可以省略呢

问题描述:

Don't use words,expressions,or phrases____only to people with specific knowledge.
A being known
B having been known
C to be known
D known
为什么 还有D是现在完成时的被动语态吗?
有人说:其实这个句子写成定语从句,是这样:Dont't use words,expressions,or phrases that are known only to people with specific knowledge.
我们可以把that are 省略。
为什么that are 可以省略呢