单项选择题

(66)is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group.(67)is an error detection code that most data conlmunication networks use.(68)is an interior gateway protocol that uses a distance vector algorithm to propagaterouting information.(69)is a transfer mode in which all types of information are organized into fixed form cells on all asynchronous or nonperiodic basis over a range of media.(70)is an identifier of a web page.

A.ISDN
B.x.25
C.Frame Relay
D.ATM
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