The chairman requested that ＿＿＿＿＿＿＿＿＿＿＿. A. the members studied the problem more carefully

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A. the members studied the problem more carefully
B. the problems were more carefully studied
C. the problems could be studied with more care
(答案→)D. the members study the problem more carefully
解析：在suggest, demand, request，require(要求)，order(命令),insist（坚持），advise（劝告）等动词之后的宾语从句中，谓语动词要用(should) do，同时还应注意语态。