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问题 单项选择题

5种药物的LD50和ED50值如下所示，最有临床意义的药物是

A．LD50：30mg/kg，ED50：25mg/kg
B．LD50：30mg/kg，ED50：15mg/kg
C．LD50：30mg/kg，ED50：5mg/kg
D．LD50：30mg/kg，ED50：10mg/kg
E．LD50：30mg/kg，ED50：6mg/kg

答案

参考答案：C

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．binarytext

B．hypertext

C．plaintext

D．supertext
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问答题 简答题

影响我国牛肉竞争力的因素有哪些？
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