问题补充：
It is he often fails in exams makes his parents worried about him.
A. what；that.
B. that；what.
C. that；that.
D. because；that.
答案：
A. what；that.
B. that；what.
(答案→)C. that；that.
D. because；that.
解析：考查主语从句和强调句型。强调句型的基本结构为：It is/was被强调成分that/who其它成分。其最大的特点是把it is/was…that/who…去掉以后，句子仍然是成立的。本题强调的是that引导的主语从句，在名词性从句中that只起引导作用，在句中不充当任何成分。句意：就是他经常考试不及格才让他的父母亲很担心他。故C正确。
