Mr. Brown is one of teachers in the school. All the students like him.A. the most popular

问题补充：

Mr. Brown is one of teachers in the school. All the students like him.

A. the most popular

B. the least popular

C. the more popular

D. the less popular

答案：

(答案→)A. the most popular

B. the least popular

C. the more popular

D. the less popular

解析：the most popular最受欢迎的；the least popular最不受欢迎的；比较级前一般不搭配定冠词the使用。联系下文，所有学生都喜欢它。可知前文指的是，布朗先生是学校里最受欢迎的老师之一。结合语境可知选A。