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What can be concluded about "modem" ?A．It converts data from one form. to another.B．It will be out of date soon.C．It serves as a link between senders and recipients of message.D．It transmits message more efficiently than other devices.

题目

What can be concluded about "modem" ?

A．It converts data from one form. to another.

B．It will be out of date soon.

C．It serves as a link between senders and recipients of message.

D．It transmits message more efficiently than other devices.

参考答案和解析
正确答案：A
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相似问题和答案

第1题：

What can be inferred from Paragraph 4?

A. Unpackaged products are of bad quality.

B. Supermarkets care more about packaging.

C. It is improper to judge quality by packaging.

D. Other products are better packaged than food.


正确答案：C

推理判断题。第四段讲述了人们对于包装不好的物品的固有认识，即：人们普遍认为包装不好的物品质量肯定差，所以C项应为正确答案。

第2题：

One can never find out what the other people think about from his facial expression.

A、It means "wearing the mask"

B、It means "keeping ideas to herself"

C、It means "telling everyone her bright ideas"

D、It means "agreeing with others’ ideas"


参考答案：A

第3题：

An activity has an early start date-of the lOth and a late start date of the 19th. The activity also has a duration of 4 days. There are no nonworkdays. From the information given, （）what can be concluded about the activity?

A.Total float for the activity is 9 days.

B.The early finish date ofthe activity is the end ofthe day on the 14th.

C.The late finish date is the 25th.

D.The activity can be completed in 2 days ifthe resources devoted to it are doubled.


参考答案：A

第4题：

What can be concluded from the passage?

A. A fuelling ambition plays a leading role in one’s success.

B. A responsible adviser is more important than the knowledge of writing.

C. As to the growth of a genius, I.Q. doesn’t matter, but just his/her efforts.

D. What really matters is what you do rather than who you are.


正确答案：D

第5题：

Digital data can also be represented by (71)signals by use ofa modem. The modem converts a series of binary voltage (72) into an analog signal by encoding the digital data ontoa carrier frequency. The resulting signal occupies a certam spectrum of (73) centered about the carTier and may be propagated acrossa medium suitable for that carrier. The most common modems represent digital data in the voice(74)and hence allow those datato be propagated over ordinary voice-grade (75 )lines At the other end of the line, another modem demodulates the signal to recover the original data

(71)

A.analog

B.digital

C.Modem

D.electric


正确答案：A
数字数据也可以通过调制解调器用模拟信号来表示。调制解调器把数字数据编码为一种载波频率，从而可以把二进制电压序列转换为模拟信号。产生的信号占用了以某一频率为中心的载波频带，可以通过适合于该载波的介质进行传播。大多数通用的调制解调器表示话音频带的数字数据，因而允许这些数据在通常的话音级电话线路上传播。在线路的另一端，另外一个调制解调器对信号进行解调并恢复原来的数据。

第6题：

What information can parents probably get about their children at family dinner? (no more than 12 words)

_________________________________________________________________


正确答案：

their children’s school performance, daily activities and attitudes toward life

第7题：

Networks can be interconnected by different devices. In the physical layer, networks can be connected by(66)or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept(67), examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have(68)network layer, the router may be able to translate between the packet formats. In the transport layer we fmd transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message(69). As an example, gateways between Internet e-mail and X.400 e-mail must(70)the e-mail message and change various header fields.

A．repeaters

B．relays

C．connectors

D．modems


正确答案：A
解析：网络可以用不同的设备互连。在物理层，用中继器或集线器互连，这些设备只是在相同的网络之间传关比特串。在上面的数据链路层，可以使用网桥或交换机，这些设备接收数据帧，检查MAC地址，并可以实现少量的协议转换，把数据帧转发到不同的网络中。在网络层，我们使用路由器连接两个网络。如果两个网络的网络层不同，路由器能够对分组格式进行转换。在传输层，我们使用传输网关，它可以在两个传输连接之间建立接口。最后，在应用层，应用网关实现消息语法之间的翻译。例如，在Internet邮件和X.400邮件之间的网关可以对邮件报文进行语法分析，对报文的各个报头字段做出改变。

第8题：

What do we know about Olivetti ?

A.It produced the best typewriter in the word.

B.It designed the word’s first mainframe. computer.

C.It exported more typewriter than other computer.

D.It has five independent companies with its head office in lvrea.


正确答案：D

第9题：

What is the difference between a CSU／DSU and a modem?()

A. A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line.

B. A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line.

C. A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line.

D. A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line.


参考答案：D

第10题：

（71）is the science of hiding information。Whereas the goal of cryptography is to make data unreadable by a third party。the goal of steganography is to hide the data from a third party。In this article,I will discuss what steganography is,what purposes it serves,and will provide an example using available software。

　　There are a large number of steganographic（2）that most of us are familiar with(especially if you watch a lot of spy movies),ranging from invisible ink and microdots to secreting a hidden message in the second letter of each word of a large body of text and spread spectrum radio communication。With computers and networks,there are many other ways of hiding informations,such as:

　　Covert channels(c,g,Loki and some distributed denial-of-service tools use the Internet Control（3）Protocol,or ICMP,as the communication channel between the“bad guy”and a compromicyed system)

　　Hidden text within Web pages

　　Hiding files in“plain sight”(c,g，what better place to“hide”a file than with an important sounding name in the c:\winnt system32 directory)

　　Null ciphers(c,g,using the first letter of each word to form a hidden message in an otherwise innocuous text)

　　steganography today,however,is significantly more（4）than the example about suggest,allowing a user to hide large amounts of information within image and audio。These forms of steganography often are used in conjunction with cryptography so the information is double protected;first it is encrypted and then hidden so that an advertisement first。find the information(an often difficult task in and of itself)and the decrypted it。

　　The simplest approach to hiding data within an image file is called（5）signature insertion。In this method ,we can take the binary representation of the hidden data and the bit of each byte within the covert image。If we are using 24-bit color the amount and will be minimum and indiscriminate to the human eye。

（73）处的单词应是

A.Member
B.Management
C.Message
D.Mail

答案：C
解析：
译文如下：
信息隐藏学是隐藏信息的科学。而密码学的目的是让数据对于第三方不可识别，而信息隐藏学的目的则是将数据对于第三方隐藏起来。本文，我将论述信息隐藏学是什么、它的目的是什么，并且会提供使用可行软件的案例。
有许多信息隐藏的方法实际上我们都很熟悉（特别是如果你看过一些谍战片！），从隐型墨水和微小的点点，到将信息暗含在一大段文字的每个单词的第二个字母中，还有无线通信中的扩频技术等等。使用计算机和网络，有许多其他的隐藏信息的方法，比如：
转换信道（e.g.，洛基和一些分布式拒绝服务工具使用网际控制管理协议，或叫做icmp，作为“坏人”和受攻击的系统之间的通信信道）
隐藏信息在网页中
隐藏文件在“眼皮儿底下”（比如，隐藏信息在什么地方比给它取一个重要的熟悉名字放置在目录Ｃ：\winnt\system32中更好？）
空域算法（比如，使用一段毫不相干的文字中每个单词的首写字母来表示一个隐藏的信息）
隐写术在今天，然而明显比上面的例子更强大，允许用户隐藏大量的信息在图像和音频文件，这些形式的隐写术通常用于结合密码学，信息是双重保护的。
最简单的方法来隐藏数据，是将信息嵌入在图像文件的像素位上（lsb），在这种方法中，我们可以把隐藏的二进制表示数据和覆盖的每个字节的图片，如果我们使用的是24位颜色，数量的变化是最小的并且肉眼是看不见的。

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