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问题 选择题

甲烷和丙烷混合气体的密度与同温同压下乙烷的密度相同，则混合气体中甲烷和丙烷的体积比是

A．2:1

B．3:1

C．1:3

D．1:1

答案

答案：D

密度之比等于相对分子质量之比。根据平均摩尔质量的计算方法得30=16×a+44×（1-a），得D。

问答题

Mr Liu entered into an agreement to buy a second-hand car from Mr Feng at a price of RMB 50,000 yuan. After the conclusion of the agreement, Mr Liu paid the price and Feng delivered the car to Mr Liu. The two parties, however, did not register the sale of the car. Following the sale Mr Liu took the car to a repair shop to repair the air conditioner. After the completion of the repair and on the way home, a fire accident occurred due to the defect of the air conditioner and caused serious damage to the car. Mr Liu returned to the repair shop claiming compensation for the defect of the air conditioner. The repair shop insisted that it was not liable for the fire accident and the resulting damage to the car. In addition, after retrieval of the data from the local vehicles registration centre, the repair shop found that the registered owner of the car was still Mr Feng, not Mr Liu. Under such a situation it refused to discuss the dispute any more with Mr Liu, on the ground that he was not a legitimate owner of the car. When Mr Liu asked Mr Feng to negotiate with the repair shop, Mr Feng was reluctant to do so on the ground that the transaction between them was over since he had duly delivered the car to Mr Liu. Required: Answer the following questions in accordance with the relevant provisions of the Property Law, and give your reasons for your answer:

(c) state whether the repair shop should be liable for the damaged car if the fire was caused by the defect of the air conditioner. (2 marks)
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单项选择题

下面安全套接字层协议（SSL）的说法错误的是？（）

A.它是一种基于web应用的安全协议

B.由于SSL是内嵌在浏览器中的，无需安全客户端软件，所以相对于IPSec更简单易用

C.SSL与IPSec一样都工作在网络层

D.SSL可以提供身份认证、加密和完整性校验的功能
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