当使用电子邮件访问POP3服务器时，(21)。

(92)

(91)

(90)

(89)

(87)

For each blank, choose the best answer from the four choices and write down on the answer sheet.

  (71) is a channel's capacity which directly reflects the data transfer rate of the channel.

  (72) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.

  (73) is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication.

  (74) is a transfer mode in which all types of information are organized into fixed form. cells on an asynchronous or non-periodic basis over a range of media.

 Ethernet is the popular LAN developed under the direction of the (75).

(85)

(86)

(84)

下列操作系统中，(47)没有网络功能。Windows　95/98下，下面选项中(48)不正确。对于Windows　NT而言，(49)。Windows　NT中的Internet信息服务中(IIS)，通常不包括(50)服务。设置网卡端口地址的目的是(51)。