—How do you improve your listening skill Mary?—I often do it tapes and English radios.A.

问题补充：

—How do you improve your listening skill, Mary?

—I often do it tapes and English radios.

A. by hearing

B. in listening to

C. by listening to

D. for listening

答案：

A. by hearing

B. in listening to

(答案→)C. by listening to

D. for listening

解析：考查固定结构。By doing sth通过某种方式或手段。Listen是不及物动词，后跟宾语是要和to连用。所以选C。