应用层可以提供基本的安全服务，只能单独提供，不能联合提供。
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When learning a new route, if a LSA received is not found in the topological database, what will an internal OSPF router do?（）
A. The sequence numbers are checked, and if the LSA is val id it is entered into the topology database.
B. The LSA is placed in the topological database and an acknowledgement is sent to the transmitting router.
C. The LSA is dropped and a message is sent to the transmitting router.
D. The LSA is flooded imme diately out of all the OSPF interfaces, except the interface from which the LSA was received.
先行登记保存的证据，应当加封工商行政管理机关先行登记保存封条，由工商行政管理机关保存。
A. 正确
B. 错误
Positions read from this chart should，to agree with chart 3949，be （） 0.03 minutes Northwards and 0.22 minutes Westwards．
A. shifted
B. removed
C. changed
D. altered
敞流式流量计：以稳定的速度移动仪器，连续的沿井深进行测量流动剖面；可测量的流量范围小。
A. 正确
B. 错误
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