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问题 单项选择题

传染病流行必须具备三个基本环节，切断任一环节则不能造成流行。接种疫苗是从（）环节阻止传染病流行

A.易感动物

B.传染源

C.传播途径

D.传播媒介

E.以上都不是

答案

参考答案：A

单项选择题

客运车辆转籍、过户后，拟继续从事道路旅客运输经营的，车辆的新所有人应当凭车辆转籍、过户证明和车辆档案，向转入地的道路运输管理机构（）经营行政许可或配发《道路运输证》。

A.登记

B.备案

C.告知

D.重新申请
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单项选择题

Networks can be interconnected by different devices in the physical layer networks can be connected by (71) or hubs．which just move the bits from one network to an identical network．One layer up we find bridges and switches which operate at data link layer．They can accept (72) ，examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process in me network layer，we have routers that can connect two networks，If two networks have (73) network layer，the router may be able to translate betweenthe packer formats．In the transport layer we find transport gateway，which can interface between two transport connections Finally，in the application layer，application gateways translate message (74) ．As an example，gateways between Internet e-mail and X，400 e-mail must (75) thee-mail message and change various header fields．

A．analyze

B．parse

C．delete

D．create
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