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问题 选择题

岸上的人观察到下列现象中属于光的折射的是（　　）

A．水上的荷花

B．水中的山的倒影

C．水中的月亮

D．水中游动的鱼

答案

A、水上的荷花反射的光进入人的眼睛，人就看见了荷花，这是光的反射现象；

B、水中山的倒影是岸上山的光经水面反射形成的虚像，属于光的反射现象；

C、水中月亮是月亮的光经水面反射形成的虚像，属于光的反射现象；

D、我们看到的水中游动的鱼是鱼的光经水面发生折射进入我们眼睛，我们逆着折射光线看到的虚像，这是光的折射现象；

故选D

单项选择题

开放式基金的基金份额的申购、赎回和登记，由（）负责办理。

A.基金托管人

B.基金管理人

C.证券登记结算中心

D.商业银行
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单项选择题

(71) is used to ensure the confidentiality, integrity and authenticity of the two end points in the private network. (72) , 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 alsohandles the exchange of session keys used for that one transaction.
Networks that use (73) to secure data traffic can automatically authenticate devices by using (74) , which verify the identities of the two users who are sending information back and forth. IPSeccan be ideal way to secure data in large networks that require secure connections among many devices.
Users deploying IPSec can (75) their network infrastructure without affecting the applications on individual computer. The protocol suite is available as a software-only upgrade to the networkinfrastructure. This alows security to be implemented without costly changes to each computer. Mostimportant, IPSec allows interoperability among different network devices, PCs and other computingsystems.

A．characteristics
B．associated links
C．digital certificates
D．attributes
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