保温瓶瓶胆内壁涂有水银，主要是为了防止( )。
A．热的蒸发
B．热的传导
C．热的辐射
D．热的对流
参考答案：C
解析：[命题提示]
本题主要考查考生对保温瓶的原理的了解
[解题要点]
考生应多注意观察生活中的各种设计，分析其原理
[答案与解析]
保温瓶瓶胆内壁涂有水银，热水热量在向外流失的过程中又会有一大部分被水银反射回来，从而能起到保温效果。故选C。
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| Jose is a student at a medical college. He is going to work in a hospital as a 1 . Jose lives at home with his parents, a disabled (残疾的) elder sister and two younger brothers. Both his parents have full-time jobs and Jose has a/an 2 job in a restaurant to help the family after class. Several weeks ago Jose's father didn't feel 3 . When he went to a doctor. he was told that there was something wrong with his heart and he needed to be operated on (做手术) and would have to give up his 4 for at least one year. Faced with the large medical expenses (医疗费) and loss of almost two thirds of the family's income for the next year, Jose's mother wanted him to drop out of 5 and do more work to help the 6 . Jose loves his family very much and 7 the sacrifices (牺牲) they have made for his education, but, if he drops out now, he will lose the whole term's credit (学分). That will be too much for 8 . He doesn't know what to do. He spoke to his girl friend, Maria, and she told him to go on his study in school. He 9 spoke to his uncle, Carlos, but he thought that his first 10 was to help his family get through the difficult time ahead. What should Jose do? | ||||
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