His mother looked very tired，for she the house herself all day.
A. had cleaned
B. has been cleaning
C. had been cleaning
D. has cleaned
网友回答
A. had cleaned
B. has been cleaning
(答案→)C. had been cleaning
D. has cleaned
解析：考查完成进行时。根据关键词all day可知应该使用完成进行时。再根据上文的looked可知应该使用过去完成进行时。