— What are you mailing, Tom?

— A textbook ______ a new method of teaching physics. I want my friend to take a look at it.

[      ]

A. is based on

B. based on

C. basing on

D. which based on

PMK可编程调节器共有三类模块，它们分别是输入模块、控制运算模块和输出模块。