单项选择题 In the strength of the carrier signal is varied to represent binary 1 or 0. (72) is a system that can map a name to an address and conversely an address to an name. (73) is a three-way handshaking authentication protocol that it's packets are encapsulated in the point-to-point protocol (74) is an approach that enables an ATM Switch to behave like a LAN switch. (75) is an guided media which is made of glass or plastic and transmits signals in the form. of light.A．ASKB．PSKC．FSKD．FDM

多项选择题 社会化的内容主要有（）。

单项选择题 一个复杂的系统可由若干个简单的系统串联或并联构成。已知两个简单系统I和J的失效率分别为λI＝25×10-5/h和λJ＝5×10-4/h，则由I和J经如图1所示的串联和并联构成的复合系统P和Q的失效率分别为πP＝(5)/h和πQ＝(6)/h，平均无故障时间分别为MTBFp＝(7)h和MTBFQ＝(8)h。系统P开始运行后2万小时内能正常运行的概率RP＝(9)。A．25×10-5B．33×10-5C．66×10-5D．75×10-5