The reason I have to go is my mother is ill in bed.
A. why...why
B. why...because
C. that...because
D. why...that
网友回答
A. why...why
B. why...because
C. that...because
(答案→)D. why...that
解析：考查定语从句和表语从句：句意：我不得不走了的原因是我母亲生病在床。the reason后面跟一个定语（从句），The reason is that my mother is ill in bed. 用why引导定语从句，第二空是表语从句的连接词：原因是什么？是一个事实，这个事实用that引导，选D。