搜题请搜索小程序“爱下问搜题”
问题 选择题

Our school has about 100 computers, but only sixty percent ____ used regularly.

A．is

B．are

C．was

D．were

答案

B

题目分析：句意：我们的学校有100台电脑，但是通常地仅仅有6%被使用。这里sixty percent 后面省略了of 100 computers，谓语动词的单复数，根据介词of后的名词来确定，这里名词是可数名词，当然谓语动词用复数，根据前面的动词可知这里也应该用一般现在时，故选B。

考点：

填空题

Sn是等差数列{an}的前n项和，若a2+a4+a15是一个确定的常数，则在下列各数中也是确定常数的项是______（填上你认为正确的值的序号）

①S7②S8③S13④S16．
查看答案
单项选择题

The network layer provides services to the transport layer. It can be based on either（71）. In both cases，its main job is （72） packets from the source to the destination. In network layer，subnets can easily become congested，increasing the delay and（73）for packets. Network designers attempt to avoid congestion by proper desing,Techniques include （74） policy，caching，flow control，and more. The next step beyond just dealing with congestion is to actually try to achieve a promised quality of service. The methods that can be used for this include buffering at the client，traffic shaping，resource（75），and admission control. Approaches that have been designed for good quality of service include integrated services (including RSVP), differentiatd services, and MPLS.

空白处（75）应选择（）

A．distribution

B．guarantee

C．scheme

D．reservation
查看答案