I can't find Mary downstairs.She ____ her homework upstairs.A must do Bmust be doing C must havedone Dcan't do答案是B,为什么不选A

分类: 作业答案 • 2022-06-23 22:04:37

问题描述：

I can't find Mary downstairs.She ____ her homework upstairs.A must do Bmust be doing C must have
done Dcan't do答案是B,为什么不选A

答

因为回答的时候Mary正在楼上做作业，所以用进行时。
而A是现在时，不符合语境。

答

他是说玛丽一定正在做作业,所以我现在找不到玛丽啊.be doing是现在进行时,所以选B更加贴切