UC知道情态动词：She must have gone back to the vally。
来源：百度知道 编辑：UC知道 时间：2024/05/28 15:10:46
－She must have gone back to the vally。
－No,she ___ the entrance to iy was no where to be found.
A mustn't B couldn't C hadn't
答案 B
为什么
－No,she ___ the entrance to iy was no where to be found.
A mustn't B couldn't C hadn't
答案 B
为什么
情态动词must在否定中不能用mustn’t。而且该句must对应的否定词只有couldn’t。所以选B
must have +动词的过去分词是对过去动作的推测。must用于推测性用法时，只用于肯定句。疑问句和否定句用can 或could.这句话中，是否定的回答，所以用couldn't.
B 意思是她“不可能”，山谷的入口找不到
couldn't意思是不可能
一般否定句和疑问句用can，肯定句用must
C hadn't