The Border Gateway Protocol (BGP) is an interautonomous system （） protocol. The primary function of a BGP speaking system is to exchange network （） information with other BGP system. This network reachability information includes information on the list of Autonomous System (ASs) that reachability information traverses. BGP-4 provides a new set of mechanisms for Supporting （） interdomain routing. These mechanisms include support for advertising an IP （） and eliminate the concept of network class within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes, including （） of AS paths. These changes provide support for the proposed supernettting scheme.

BGP-4 provides a new set of mechanisms for Supporting （） interdomain routing.

A．answerless

B．connectionless

C．confirmless

D．classless

造成接触不良的主要原因是电气接头表面污损，接触电阻（）。

A.减小

B.增大

C.不变

D.短路