We consider it necessary that a plan before doing the work.
A. is made
B. will be made
C. should be made
D. made
网友回答
A. is made
B. will be made
(答案→)C. should be made
D. made
解析：is made是一般现在式；will be made是将来时态；should be made表示应该；made是一般过去式。Should是情态动词，（表示义务，责任）意思是应该，计划被制定所以用被动式。句意是我们考虑到做工作前应该先制定计划是必要的。故选C.