Years ago we didn't know this, but recent science study that people who don't sleep well soon get ill.
A. showed
B. will show
C. has shown
D. is showing
网友回答
A. showed
B. will show
(答案→)C. has shown
D. is showing
解析：考查时态，句意：多年前，我不知道这个，但是最近的研究表明睡眠不好的人很容易生病。句中的recent 可知应用现在完成时。选C。