问题描述：
有关情态动词的1个句子
i saw Mary in the library yesterday .
you can't have seen her ,she is still in hospital.
为什么用完成式呀?
__turn_down the radio ,dthe baby's asleep in the next room.
为什么不用不定式呀,不是关掉表示目的吗?
have you any idea why she did it 为什么用why
i saw Mary in the library yesterday .
you can't have seen her ,she is still in hospital.
为什么用完成式呀?
__turn_down the radio ,dthe baby's asleep in the next room.
为什么不用不定式呀,不是关掉表示目的吗?
have you any idea why she did it 为什么用why
问题解答：
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