单项选择题
The major problem with E-mail is that it is （1） easy to use that people can become （2） with messages （3） they can possibly answer in a day. In addition, mail boxes require some management to （4） messages or archive those that might be required later. Senders don’t always know about your E-mail backlog and often send （5） messages.
（3）处应选择（）
A.more than
B.than
C.that
D.which