问题
选择题
—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
答案：C
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。