对于掺用缓凝型外加剂、矿物掺合料或有抗渗性要求的混凝土，覆盖浇水养护的时间不得少于（

由于金银具有如下的天然属性，适于充当一般等价物()。

A.质地均匀，其表现价值的尺度很容易统一

B.便于分割和携带，适合充当交换媒介

C.贵金属体积小，价值高。符合交易的需要

D.不是生产过程的必需原材料，用于货币材料不影响经济发展

E.贵金属的稀有性

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．

（72）处应填（）。

A．computers

B．routers

C．switches

D．networks

如果a÷b=4，那么a和b成______比例关系．

看施工图，一定要把平面图、立面图、剖面图结合起来，搞清三者关系。

在系统中，反馈是把（）反过来馈送给（），反馈是（）和（）的逆向联系。