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问题 填空题

从海水中提取镁盐，通常将______加入海水中或卤水中，沉淀出______，______与盐酸反应生成______，______熔融状态的氯化镁，就能制的金属镁，转化过程中发生的化学反应主要是______；______；______．本题没有涉及的化学基本反应类型是______．

答案

从海水中提取镁盐，通常将熟石灰加入海水中或卤水中，沉淀出氢氧化镁，氢氧化镁与盐酸反应生成氯化镁，电解熔融状态的氯化镁，就能制的金属镁．故填：熟石灰；氢氧化镁；氢氧化镁；氯化镁；电解．

转化过程中发生的化学反应主要有：Ca（OH）2 +MgSO4═Mg（OH）2↓+CaSO4，Mg（OH）2+2HCl═MgCl2+2H2O，MgCl2

 通电 
.
 
Mg+Cl2↑．

本题没有涉及的化学基本反应类型是化合反应和置换反应．故填：化合反应和置换反应．

选择题

下列各句中，加点的词语使用恰当的一句是（    ）（3分）

A．临近清明，春雨绵绵，不绝如缕，万物享受着春天的滋润，到处都勃发着生机和活力。

B．每个四中人都有自己的梦想，但奋斗才是成就事业的基石，如果只是纸上谈兵而不真抓实干，再美好的梦想也不可能成真。

C．个别公职人员对群众的合理诉求漠不关心，甚至出现了一些触及道德底线的危言危行，这应该引起有关部门的高度重视。

D．改革将转变政府职能，理清政府与市场、社会、公民间的权界关系，加强服务职能，减少审批项目等，这都与民生休戚相关。
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单项选择题

(1) is used to ensure the confidentiality, integrity and authenticity of the two end points in the private network. (2) , 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 (3) to secure data traffic can automatically authenticate devices by using (4) , 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 (5) 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.

1（）

A．Certificate

B．Encryption

C．Tunnel

D．Presentation
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