在3.1和3.2之间的小数，可以是一位小数、两位小数、三位小数…，所以有无数个小数．
故选：B．
防己的性状鉴别特征是
A．猪大肠状
B．表面弯曲处有深陷的横沟
C．断面平坦，富粉性
D．断面可见稀疏的放射状裂隙
E．气微，味淡
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
