The reason he was late for school was he had to send his mother to a hospital.
A. that; why
B. why; because
C. why; that
D. that; because
网友回答
A. that; why
B. why; because
(答案→)C. why; that
D. that; because
解析：句意：他为什么会上学迟到的原因是他不得不送妈妈去医院。第一空填why。引导定语从句，先行词是reason，定语从句中缺少原因状语，第二空填that，连接表语从句，当主语是the reason的时候，表语从句用that连接，所以选C。