The reason _____ he was late for school was _____ he had to send his mother to a hospital.A. that; whyB. why; becauseC. why; thatD. that; because

本题考查同位语从句和表语从句的连接词选择。

1. 第一空：修饰名词reason，需用why引导同位语从句，表示原因。
2. 第二空：连接表语从句，需用that，强调事实或结果。
   关键点：区分同位语从句与表语从句的连接词，注意because不能引导表语从句。

第一空分析

The reason后接同位语从句，解释原因。

• 若从句强调原因，需用why引导，如：
  The reason why he was late is that he had an accident.
• 若从句仅补充说明，可用that，但本题从句明确说明原因，故选why。

第二空分析

was后接表语从句，需用that引导，表示事实。

• because不能引导表语从句，排除含because的选项（B、D）。
• why在此处不符合逻辑，排除A。