The reason he gave for being absent from school was he had to attend his sick mother at

问题补充：

The reason he gave for being absent from school was he had to attend his sick mother at home.

A. which; because

B. why; because

C. 不填; that

D. why; that

答案：

A. which; because

B. why; because

(答案→)C. 不填; that

D. why; that

解析：先行词为表原因的the reason, 且从句中的gave缺宾语, 所以第一空用关系代词that 或which用作gave的宾语, that 或which可以省略; 第二空是由that引导的表语从句, 即The reason …is/ was that…句式。