I have an English problem!Need your help!

问题描述:

I have an English problem!Need your help!
The best method(_)is(_)it.
A.learning language,to use
B.to learn a language,by using
C.of learning English,using
D.to learn English,use
P.S.我觉得B和C都对……选哪个说明下理由哈!

通过什么学习用介词by
the best way to do=the best way of doing
C选项少了介词by