Before you leave the lab,the doors and windows _shut in case

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Before you leave the lab,the doors and windows _shut in case of rain.A.is B.are C.is to be D.are to be
选哪个,为什么选哪个

D,are用于复数,系动词+ to be表示“要”的意思
比如man is to die ,人总要死的
再问：能在详细一点吗
再答：你是指哪个要详细点？这句话的意思是，你走之前，要把实验室的门和窗户关上以防下雨。 A和B都是系动词，如果要选这个，句子应该是：make sure that the doors 。。。。。。are shut。。。 C和D是一个句式，系动词+ to be表示“要”的意思，这里 the doors and windows 是复数，故而选are

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