i often have conversations with John by __ E-mail,while i keep in touch with tom over __ telephone.

题目

i often have conversations with John by __ E-mail,while i keep in touch with tom over __ telephone.
A the the B an the C the a D / the

答案

by的用法之一
表示用交通工具、通讯工具后接名词单数,不加冠词.
选吧D