[单项选择]

Communication via e-mail is by far the most common Internet activity. You can (71 ) with anyone in the world who has an Internet address or e-mail (72) with a system connection to the Internet. All you need is (73) the Internet and an e-mail program. Two of the most widely used e-mail programs are Microsoft’s (74) and Netscape’s Navigator. A typical e-mall message has three basic (75) : header, message, and signature.

（74）处填（）。
A. Yahoo
B. Explore
C. Foxmail
D. Outlook Express

By far the most common difficulty in study is simple failure to get down to regular concentrated work. This difficulty is much greater for those who do not work to a plan and have no regular routine of study. Many students muddle along, doing a hit of this subject or that, as the mood takes them, or letting their set work pile up until the last possible moment.
Few students work to a set time-table. They say that if they did construct a timetable for themselves they would not keep to it, or would have to alter it constantly, since they can never predict from one day to the next what their activities will be. No doubt some temperaments take much more kindly to a regular routine than others. There are many who shy away from the self-regimentatign of a weekly time-table, and dislike being tied clown to a definite programme of work. Many able students claim that they work in cycles. When they become interested in a topic they work on it intensively for three or four days at a
A. when they have the energy
B. when they are in the mood
C. when they find conditions suitable
D. when they feel fit