Yearsagowedidn'tknowthis,butr

发布时间：2020-07-09 22:29:10

Years ago we didn't know this, but recent science ________ that people who don't sleep well soon get ill．













A.showed












B.has shown











C.will show











D.is showing

网友回答

B解析根据but表示的转折意义判断，后面应说明现在的情况，与几年前相对照，并且空后说明了结果，所以应用现在完成时。
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