第15题: [单项选择]ITU标准OC-3的数据传输速率为______。 A. 51.84 Mbps B. 155.520 Mbps C. 622.080 Mbps D. 1.244 Gbps 参考答案:B 答案解析:[解析] 无源光纤网(PON)在ITU G.983建议中标准化的,分为两个部分:①OC-3,155.520Mbps的对称业务;②上行OC-3(155.520Mbps)、下行OC-12(622.080M
第24题: [单项选择]According to the writer, "interstellar travel" serves as __________. A. a practical way to escape the end of the world B. nothing more than postponing the end of the world C. a way hopping from planet to planet D. a way to escape from gravity 参考答案:B 答案解析:事实细节题。根据文章第二段第二句话的后半句“but the mightiest of starships could do no more than suspend the end of the wo
第25题:[单选题] 二节拉梯的工作长度为( ) A. 3m±0.1m B. 3.5m±0.1m C. 2.5m±0.1m D. 2m±0.1m 参考答案:A