问题
选择题
The manager is talking with his secretary _____ the telephone. They usually keep in touch _____ telephone.
A．by ;on
B．through; by
C．on; on
D．by ;with
答案
答案：B
考查介词的用法。by当“通过”讲时，其后不加冠词；through当“通过”讲时，其后加冠词。