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
网友回答
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。