The Border Gateway Protocol (BGP) is an interautonomous system. ___49___ protocol. The primary function of a BGP speaking system is to exchange network ___50___ information with other BGP system. This network reachability information includes information on the list of Autonomous System (ASs) that teachability information traverses. BGP-4 provides a new set of mechanisms for supporting ___51___ interdomain routing. These mechanisms include support for advertising an IP ___52___ and eliminate the concept of network class within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes, including ___53___ of AS paths. These changes provide support for the proposed supernettting scheme.

50（）

A. teachability

B. scalablity

C. availability

D. reliability

食品中所含热能和营养素能满足人体需要的程度被称为（）

A.食品的营养素密度

B.食品的营养价值

C.食品的热能密度

D.食品的营养质量指数

E.以上都不是