第10题: [单项选择]Only five years ago, there ______a shortage of computer specialists. A. (A) was B. (B) were C. (C) has been D. (D) have been 参考答案:A 答案解析:The simple past tense is required. Choice (B) is past tense but does not agree with the singular sub
第16题: [单项选择]下列不属于局域网协议层次的是______。 A. 物理层 B. 数据链路层 C. 传输层 D. 网络层 参考答案:C 答案解析:[知识点] 局域网分类与基本工作原理
[评析] 局域网包含ISO/OSI参考模型中七层协议中下三层的功能,即物理层、数据链路层,由于LAN没有路由问题,一般不单独设置网络层。