题目内容
—Scientists still ________ explain exactly why people dream.
—That’s right. They might understand it all someday, but they aren’t sure now.
A.shouldn’t B.mustn’t C.needn’t D.can’t
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题目内容
—Scientists still ________ explain exactly why people dream.
—That’s right. They might understand it all someday, but they aren’t sure now.
A.shouldn’t B.mustn’t C.needn’t D.can’t