搜题请搜索小程序“爱下问搜题”
问题 选择题

铁或铝能在冷的浓硝酸中发生“钝化”，这是利用浓硝酸的（　　）

A．强酸性

B．强氧化性

C．不稳定性

D．挥发性

答案

B

“钝化”是利用浓硝酸的强氧化性，把金属表面氧化成致密的氧化物保护膜。

单项选择题

显示器分辩率指的是整屏可显示像素的多少，这与屏幕的尺寸和点距密切相关。例如15英寸的显示器，水平和垂直显示的实际尺寸大约为280mm×210mm，当点距是0.28mm时，其分辨率约为( )。

A．800×600

B．1024×768

C．1600×1200

D．1280×1024
查看答案
单项选择题

Networks can be interconnected by different devices. In the physical layer, networks can be connected by (11) 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 (12) ,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 (13) network layer, the router may be able to translate between the 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 (14) . As an example, gateways between Internet e-mail and X.400 e-mail must (15) the e-mail message and change various header fields.

15（）

A.analyze

B.parse

C.delete

D.create
查看答案