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
A. showed
(答案→)B. has shown
C. will show
D. is showing
解析：考查动词的时态。根据句子中的recent science可以知道句子中“含有过去发生的动作”对现在产生的影响。所以答案应该用现在完成时。