食物的氧热价是指A．1g食物氧化时所释放的能量B．1g食物燃烧时所释放的能量C．食物

为研究接触石棉与肺癌的关系而进行队列研究时，将石棉作业工人作为暴露组，而将另外职业的工人作为非暴露组，这种对照方法是（）

A.内对照

B.外对照

C.特异暴露人群对照

D.职业人群对照

E.一般人群对照

城市步行街（区）的主要功能效用有哪些？

=______。

非经常地为国际航行船舶服务的港口设施和处于试生产阶段的港口设施，经港口所在地港口行政管理部门同意，无需制订《港口设施保安计划》。

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 (71) algorithm．Routing protocols in internetworks differ slightly from the idealized graph model．In aninternetwork，the goal of the routers to forward packets to various (72) ．
Routers running RIP send their advertisement about cost every (73) seconds．A router also sends an update message whenever an update from another router causes it to change itsrouting 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 (74) Thus it always tries tofind the minimum hop route．Valid distances are 1 through (75) ．This also limits RIP torunning on fairly small networks．

A．6
B．10
C．15
D．16