可防止皮肤水分蒸发、促进皮肤水合的基质（）。

A．硅酮 

B．羊毛脂 

C．凡士林 

D．十二烷基硫酸钠 

E．蜂蜡

One of the most widely used routing protocols in IP networks is the Routing Information Protocol (RIP). RIP is the canonical example of a routing protocol built on the ___25___ algorithm. Routing protocols in intemetworks differ slightly from the idealized graph model. In an internetwork, the goal of the routers to forward packets to various ___26___.

Routers running RIP send their advertisement about cost every ___27___ seconds. A router also sends an update message whenever an update from another router causes it to change its routing table.

It is possible to use a range of different metrics or costs for the links in a routing protocol. RIP takes the simplest approach, with all link costs being equal ___28___. Thus it always tries to fend the minimum hop route. Valid distances are 1 through ___29___. This also limits RIP to running on fairly small networks.

29（）

A.6 

B.10 

C.15 

D.16