Question

When he saw all his books __________ here and there on the floor, he knew that something terrible

A.lying; must have happened
B.lie; must happen
C.lay; might have happened
D.had lain; could have happen

Answer 1

【答案】：A
句型”see…doing sth．”意为“看见……正在做某事”，doing有正在进行的意思，此句型指看的瞬间动作。“must+have+过去分词”表示对过去事实的肯定推测，意为“一定”，故选A。