The reason he was late for school was he had to send his mother to a hospital.
A. which; that
B. why; that
C. for which; because
D. what; why
网友回答
A. which; that
(答案→)B. why; that
C. for which; because
D. what; why
解析：考查定语从句和表语从句。本题第一空是由why引导的是定语从句，修饰名词the reason，后面定语从句的句子结构很完整，所以使用关系副词。第二空是that所引导的表语从句，that在句中不充当任何成分，只起引导和连接的作用。句意：他上学迟到的原因是他要送妈妈去医院。故B正确。