同学你好，该知识点来自沪江网校《英语零基础直达大学六级【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
T： These cars are cheap.
S： But those cars are cheaper. They are the cheapest cars I have ever seen.

T： This girl is pretty.
S： But that one is prettier. She is the prettiest girl I have ever seen.

T： These office assistants are lazy.  这里属于名词修饰名词，不需要加所有格
S： But those office assistants are lazier. They are the laziest office assistants I have ever seen.

T： This boy is thin.
S： But that one is thinner. He is the thinnest boy I have ever seen.

祝同学学习进步~