it was not possible that she _____ go down ,step by stey down the unexpected stairs into the dark be

题目

it was not possible that she _____ go down ,step by stey down the unexpected stairs into the dark below.
a.should dare b.should dare to c.must dare d.must dare to
选b,为什么to不用省略

答案

should这里情态动词,表“竟然”,dare“敢”,明显的在这里肯定是实义动词（因为前已有情态动词）了,固定搭配后要加to,