Question

【题目】Which things ______ by common people to protect the environment?
A.can be
B.can do
C.can be done
D.can be do

Answer 1

【答案】C
【解析】根据句意，which things做主语，是被动语态，情态动词的被动语态由情态动词+ be +动词的过去分词，故选C。