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问题 多选题

关于质点运动的位移和路程的下列说法正确的是（　　）

A．在某段时间内质点运动的位移为零，该质点一定是静止的

B．在某段时间内质点运动的路程为零，该质点一定是静止的

C．在直线运动中，质点的路程可能等于位移的大小

D．在直线运动中，质点的路程也可能小于位移的大小

答案

A、质点运动的初末位置重合，位移为零，但物体是运动的，故A错误；

B、路程是物体运动轨迹的长度，路程等于零，该质点一定静止，故B正确；

C、当物体做单向直线运动时，位移的大小等于路程．故C正确；

D、当物体做单向直线运动时，位移的大小等于路程，其它情况位移的大小小于路程．故D错误；

故选BC

单项选择题

在资本市场和货币市场上直接发行证券是( )。

A．资产证券化

B．二级证券化

C．融资证券化

D．四级证券化
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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 (71) algorithm．Routing protocols in internet works differ slightly from the idealized graph model．In an internet work，the goal of the routers to forward (72) to various networks．
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 its routing table．
Routing protocols use different techniques for assigning (74) 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 (75) ．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．

A．10
B．30
C．60
D．180
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