--What do you think of maths?
--My favorite. It’s for me to study of all the subjects in school.
A. more difficult
B. the most difficult
C. less difficult
D. the least difficult
网友回答
A. more difficult
B. the most difficult
C. less difficult
(答案→)D. the least difficult
解析：由the+最高级+of+可数名词复数
可排除AC
由原句My favorite.
可排除B
故选D