Question

【题目】Students _________ be careful when they do chemical experiments in the lab.

A. can B. may C. need D. must

Answer 1

【答案】D

【解析】

句意：学生在实验室做化学实验时必须小心。考查情态动词。A. can能、会；B. may可以；C. need需要；D. must必须。根据后半句when they do chemical experiments in the lab.“当他们在实验室做化学实验时”，可知前半句的句意为“学生们必须小心”，故答案选D。