Mr Li required the puter equipment referred used in every classroom.
A. should be
B. have to be
C. to be
D. to being
网友回答
A. should be
B. have to be
(答案→)C. to be
D. to being
解析：因为在表示“要求”的require, request, ask, demand等动词后的宾语从句的谓语要用“(should+)动词原形”，句中referred to是过去分词短语，作the puter equipment的定语，所以选C。