It is on September 1st students go back to school every year.
A. when
B. who
C. that
D. what
网友回答
A. when
B. who
(答案→)C. that
D. what
解析：考查强调句型。强调句型的基本结构：it is/was 被强调成分that/who其它成分。去掉it is/was…that/who…句子仍然成立。本题强调的是时间状语on September 1。句意：正是在9月七日，所有学生都返回学校。故C正确。