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问题 选择题

The number of people in Shanghai is_____than_____in Shijiazhuang.     [      ]

A. smaller; it   

B. larger; it   

C. larger; that    

D. more; that

答案

答案：C

单项选择题 A1/A2型题

引起菌群失调症的原因是（）。

A.正常菌群的增殖方式明显改变

B.生态制剂的大量使用

C.正常菌群的耐药性明显改变

D.正常菌群的遗传特性明显改变

E.正常菌群的组成和数量明显改变
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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 (41) 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 (42) , examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have (43) network layer, the router may be able to translate between the packet 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 (44) . As an example, gateways between Internet E-mail and X.400 E-mail must (45) the E-mail message and change various header fields.

A．special

B．dependent

C．similar

D．dissimilar
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