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问题 单项选择题

在雇员信息表关系EMP中，哪个属性是外键(Foreign Key)？

A．雇员号

B．雇员名

C．部门号

D．工资

答案

参考答案：C

解析：【解析】EMD的部门号与DEPT的部门号有关系，所以为外键。

填空题

锚杆（索）支护巷道，跟顶板施工的，中等冲击危险，超前支护距离不得小于（）m。
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单项选择题

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 (1) algorithm．Routing protocols in internet works differ slightly from the idealized graph model．In an internet work，the goal of the routers to forward (2) to various networks．

Routers running RIP send their advertisement about cost every (3) seconds．A router also sends an update message whenever an update from another router causes it to change its routing table．

Routing protocols use different techniques for assigning (4) to individual networks．Further, each routing protocol forms a metric aggregation in a different way．RIP takes the simplest approach，with all link costs being equal (5) ．Thus it always tries to find the minimum hop route．Valid distances are 1 through 15．This also limits RIP to runing on fairly small networks．

4（）

A．respond time

B．utilization

C．links

D．metrics
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