问题 单项选择题

Linux是目前较为流行的网络操作系统,如同Unix操作系统一样,它也可以通过手工编辑配置文件达到对系统进行配置的目的。
在Linux网络配置文件中的几个较为重要的配置文件如下:
(56) 用于存放本机主机名以及经常访问IP地址的主机名,在对IP地址进行域名解析时,可以设定为先访问该文件,再访问DNS,最后访问NIS。
Linux下存在两个网络服务守候进程的配置文件。通过修改 (57) ,可以达到关闭或开放某种对应服务的目的。以FTP服务为例,将文件中“#FTP Stream TCP nowait root/usr/ sbin/tcpd in.ftpd-1-a”前的“#”去掉就可以开启FTP服务。修改 (58) ,可对允许访问本机提供服务的主机范围进行限制。例如在文件中加入“in.ftpd:202.112.207.0/ 255.255.255.0”就可以允许202.112.207.0子网的用户主机访问本机提供的FTP服务。
在Linux下进行DNS服务时, (59) 是控制解析器配置的最主要文件,规定了解析使用的服务,以及服务的顺序,比如可以通过在文件中加入"Order hosts,DNS,NIS"设定前面提到的域名解析顺序; (60) 是配置DNS服务器的主要文件,指定了本机使用的域名服务器以及多个服务器之间查找的顺序等。

A./etedserviees.conf

B./etc/’metd.conf

C./etc/services

D./etc/host.conf

答案

参考答案:B

单项选择题

A total of 4.6 million digital televisions have been sold, and the sales of HDTV sets have quadrupled since last year. Consumers have bought HDTVs to play their DVDs and to have clearer pictures and wide screens. Only a small percentage of the people who have purchased HDTVs, however, have actually hooked their TVs up to receive high-definition television digital signals. Perhaps television viewers are having trouble keeping up with the changes in technology. Even the manufacturers of HDTVs, like Mitsubishi, Thomson Multimedia, Sony, and Samsung seem to have a tough time learning how to make their sets work with the various digital TV formats because little standardization has been required or implemented in the industry.

Some of the HDTVs weigh over 200 lbs., and a variety of retailers offer a delivery service to the buyer’s home to help install the heavy sets. This is known as a white-glove service and usually comes with an extra fee. After HDTV purchasers get their sets home and hook them up, they will still need to work to get the digital signals to their systems. Most of the industry’s cable providers do not yet offer high~definition programing, and only about 15% of commercial television stations have switched over to even the lowest improved digital pictures. Worse yet, viewers may need to install antenna before they can even get the digital signals to their new HDTV sets. Another frustration for home-theater seekers is that the current HDTV sets allow owners only to watch high-definition programs, not to record them.

On the whole, this passage is positioned to dwell on ().

A. the overall picture of the HDTV sector

B. how the giant TV makers should offer better products

C. a lament over consumers’ inability to use a high-end TV set

D. a criticism of the TV makers for doing nothing about a big problem

多项选择题