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问题 问答题 简答题

有一只220V的电灯泡，灯泡的电阻是484Ω，当电源电压为220V时，求通过灯泡的电流？

答案

参考答案：通过灯泡的电流I=U/R=220/484=0.455（A）

选择题

—What does her boyfriend look like?      

—______.        [      ]

A. He is intelligent and confident        

B. He likes playing football        

C. He is quite tall with curly hair        

D. He is very good
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单项选择题

In a public-key cryptosystem, (71) encrypted with the public key can only be deciphered with the private key from the same (72) . Conversely, (71) encrypted with the private key can be decrypted only with the public key. Users can make their public keys (73) available or place them at a key distribution center or others to access. However, the private key must be (74) safe. In public-key systems there’s no (75) to find a safe channel for communicating a shared secret key.

A. more B. necessary C. need D. space
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