第17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24题: [单项选择]按香农定理,如果信号与噪声功率比S/N=1000,带宽B=3000Hz,则数据传输最大速率约为 ______。 A. 30Kbps B. 30bps C. 300Kbps D. 3Kbps 参考答案:A 答案解析:[知识点] 数据通信技术
[评析] 香农定理指出;在有随机热噪声的信道上传输数据信号时,数据传输速率Rmax与信道带宽B、信号噪声功能比S/N关系为:Rmax=B·log2 (1+S/N)