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问题 单项选择题

公安消防队和（）依照国家规定承担重大灾害事故和其他已抢救人员生命为主的应急救援工作。

A、专职消防队

B、志愿消防队

C、民间消防组织

D、村或社区义务消防队

答案

参考答案：A

选择题

欧洲流经国家最多的河流是[ ]

A．莱茵河

B．伏尔加河

C．乌拉尔河

D．多瑙河
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单项选择题

The network layer provides services to the transport layer．It can be based on either (67) ．In both cases，its main job is (68) packets from the source to the destination．

In network layer，subnets can easily become congested，increasing the delay and (69) for packets．Network designers attempt to avoid congestion by proper design．Techniques include (70) policy,caching，flow control，and more．

The next step beyond just dealing with congestion is to actually try to achieve a promised quality of service．The methods that can be used for this include buffering at the client，trafficshaping，resource (71) ，and admission contr01．Approaches that have been designed forgood quality of service include integrated services(including RSVP)，differentiated services，andMPLS．

70（）

A．abandonment

B．retransmission

C．checksum

D．synchronism
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