单选题 In (66) the strength of the carrier signal is varied to represent binary 1 or 0. (67) is a system that can map a name to an address and conversely an address to al name. (68) is a three-way handshaking authentication protocol that it's packets are encapsulated in the point-to-point protocol. (69) is an approach that enables an ATM switch to behave like a LAN switch. (70) is an guided media which is made of glass or plastic and transmits signals in the form of light.

【正确答案】 A
【答案解析】本题主要考查调制的专业术语。ASK为幅度键控，PSK为移项键控的英文缩写，FSK为移频键控的英文缩写，FDM为频分多路复用的英文缩写。答案为A。
【正确答案】 D
【答案解析】本题主要考查域名系统的缩写DNS。NAT是Network能Address Translation的缩写。NCP是Network Core protocol的缩写。DDN是Digital Data Network的缩写。答案为D。
【正确答案】 C
【答案解析】CHAP为Challenge Handshake Authentication Protocol的缩写，中文译为挑战握手认证协议。PPP是点对点协议的缩写。LCP是链路控制协议的缩写。PAP是密码认证协议的缩写。答案为C。
【正确答案】 B
【答案解析】VLAN为虚拟局域网。LANE是指在ATM上的局域网仿真。VPN为虚拟个人网络。IPOA是IP Over ATM的缩写，是在ATM-LAN上传送IP数据包的一种技术。答案为B。
【正确答案】 B
【答案解析】Optical fiber译为光纤。Coaxial cable为同轴电缆。Unshielded Twisted-pair Cable为非屏蔽双绞线。Shielded Twisted-pair Cable为屏蔽双绞线。答案为B。