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
网友回答
A. being known
B. having been known
C. to be known
(答案→)D. known
解析：考查非谓语动词。不要使用那些只为那些具有专业知识的人知道的单词、句式或短语。known to 作后置定语。单词等是被知道的，故用过去分词。