There is no doubt short sight is a serious problem among the youth of our country.
A. which
B. whether
C. what
D. that
网友回答
A. which
B. whether
C. what
(答案→)D. that
解析：考查同位语从句：句意：毫无疑问在我们国家年轻人目光短浅是一个很严重的问题。doubt是同位词，that引导的是同位语从句，对doubt的内容进行说明。要注意的是如果是There is doubt就应该用whether连接同位语从句。选D。