It’s very important for students to learn a language it.A. to useB. by useC. with usingD.

问题补充：

It’s very important for students to learn a language it.

A. to use

B. by use

C. with using

D. by using

答案：

A. to use

B. by use

C. with using

(答案→)D. by using

解析：本题主要考查的是do sth by doing sth，因而本题的答案为D。