问题 单项选择题

PPP协议是数据链路层的一个协议,它被广泛用于接入Internet中。PPP协议是一个 (1) 。帧长为整数个字节。它克服了SLIP协议的缺点,可以进行协商,并且 (2) 。它可以分成3个层次,其中的网络层协议被称为 (3) ,包括了不同的网络层协议。利用PPP的优势,结合以太网产生了 (4) 协议,该协议可以通过简单的共享设备将多个客户网段接入到骨干网。若通过SLIP方式接入Internet,用户端p是 (5)

4()

A.PPTP

B.PPPoE

C.PPPoA

D.CSMA/CD

答案

参考答案:B

单项选择题
单项选择题

The average person learns most of the 30000~40000 words whose meanings he or she recognizes by hearing them or getting familiar with them in the context or simply absorbing them without conscious effort. The best way to build a good vocabulary, therefore, is to read a great deal and to participate in a lot of good talks. There are relatively few words that we learn permanently by purposefully referring to dictionaries or keeping word lists. However, even those extra few are of value, and no one will make a mistake by working on developing a larger vocabulary. Here are some suggestions of how to do it.

Read plenty of good books. When you come across a new word, or a new meaning of an old word, stop and see if you can understand it from its context. If you can’t, and if you can manage without interrupting the thought of the book too much, look it up in a dictionary or ask somebody and then repeat its meaning to yourself a couple of times. If you are really conscientious, write the word and its meaning in a personal vocabulary list—preferably using it in a sentence, or you can keep a special vocabulary notebook. Go over the list from time to time. Further, try to use a new word in writing or conversation a few times over the next several days.

Listen to good talks and be alert to new words you hear or to new meanings of words you already know. Then treat them just as you treat the new words you read.

Learn and be alert to the parts of words: prefixes, suffixes and roots. Knowing them enables you to make intelligent guesses about the meaning of words.

If you are studying a foreign language, be alert to words in that language which relate to words in English. English has inherited or borrowed much of its vocabulary of 500000~600000 words from Latin, Greek, French, Spanish and German.

The phrase“be alert to”in the third paragraph may best be replaced by“()”.

A. look at

B. pay attention to

C. write down

D. learn by heart