There is no doubt nearsightedness is a serious problem among the youth of our country.
A. /
B. which
C. whether
D. that
网友回答
A. /
B. which
C. whether
(答案→)D. that
解析：句意：毫无疑问近视在我们国家的年轻人之间是个严重的问题。There is no doubt that…毫无疑问…，doubt后面是同位语从句，因为是没有怀疑，所以后面是肯定的，用that，如果是There is doubt后面用whether连接同位语从句。选D。