问题
选择题
The reason why they failed the test was ____ they didn’t sleep at all the night before.
A．because
B．why
C．that
D．for which
答案
答案：C
题目分析：考查名词性从句。表语从句中不缺少任何成分，故用关系词that。The reason why … is/was …,……的原因是……。句意：他们考试不及格的原因是他们前一天晚上根本没睡觉。根据句意说明C正确。