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题目内容
（石家庄铁道大学大学英语1）
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
A、 showed
B、 has shown
C、 will show
D、 is showing
参考答案
