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问题 单项选择题

右图为显微镜下洋葱表皮细胞在30％蔗糖溶液中的示意图。下列叙述中错误的是（）

A．若将细胞置于清水中，A基本不变

B．若将该细胞置于20％蔗糖溶液中，B值将变小

C．B／A值能表示细胞失水的程度

D．B／A值能表示液泡体积的变化

答案

参考答案：B

单项选择题

四人参加计算机职称考试后，有以下议论：
　　甲：这次考试咱们都可过关
　　乙：咱们之中肯定有人难过关
　　丙：丁肯定可以过关
　　丁：如我能过关，我们四人肯定都能过关
　　考试结果表明四人之中有一人预测错误，那么结果是( )

A．丙的预测错误

B．丁的预测错误

C．四人都过关

D．丁没有过关
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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. (31) 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 (32) , 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 (33) 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 (34) . As an example, gateways between Internet E-mail and X. 400 e-mail must (35) the e-mail message and change various header fields.

（32）是（）

A.frames

B.packets

C.packages

D.cells
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