________one of themost important inventions of the time, the computer helps people living indifferent countries to do a lot of things.

A.Knowing tobe

B.It wasknown

C.Known as

D.As wasknown to be

答案及解析： C

解析：

computer与know之间是动宾关系，状语用过去分词，表被动。译文：计算机被认为是这个时代最重要的发明，它帮助居住在不同国家的人们做了很多事情。