搜题请搜索小程序“爱下问搜题”
问题 选择题

北方的农民常用浓烟为大白菜防冻，原因是（       ）。

A．烟雾能增强地面辐射

B．烟雾能增强大气逆辐射

C．烟雾能削弱大气逆辐射

D．烟雾能增强大气的反射作用

答案

  B

烟雾的成分能吸收地面辐射，进而增强大气逆辐射，由此可提高近地面的气温。答案为B项。

单项选择题

___39___ is used to ensure the confidentiality, integrity and authenticity of the two end points in the private network. ___40___, an application-layer protocol, authenticates each peer in an IPSec transaction. IKE negotiates security policy, determining which algorithm may be used to set up the tunnel. It also handles the exchange of session keys used for that one transaction.

Networks that use ___41___ to secure data traffic can automatically authenticate devices by using by using ___42___, which verify the identities of the two users who are sending information back and forth. IPSec can be ideal way to secure data in large networks that require secure connections among many devices.

Users deploying IPSec can ___43___ their network infrastructure without affecting the applications on individual computer. The protocol suite is available as a software-only upgrade to the network infrastructure. This alows security to be implemented without costly changes to each computer. Most important, IPSec allows interoperability among different network devices, PCs and other computing systems.

40（）

A. IPSec

B. SSL

C. L2TP

D. The Internet Key Exchange
查看答案
单项选择题 A型题

细菌代谢产物中与致病性无关的是（）。

A．内毒素

B．外毒素

C．侵袭性酶

D．热原质

E．细菌素
查看答案