问题
单项选择题
天然气管架空敷设时，经常采用冷缠聚乙烯胶粘带，既形成绝缘防腐层，又形成隔热保温层，但须在最外层包裹一层金属锡箔，金属锡箔的作用是（）
A、阻挡和反射紫外线
B、绝缘
C、美观
D、防水
答案
参考答案：A
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天然气管架空敷设时，经常采用冷缠聚乙烯胶粘带，既形成绝缘防腐层，又形成隔热保温层，但须在最外层包裹一层金属锡箔，金属锡箔的作用是（）
A、阻挡和反射紫外线
B、绝缘
C、美观
D、防水
参考答案：A
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| Time flies as an arrow. I'm already in the second half of senior grade 3 before I realized it. It is only a little more than three months before I graduate middle school. At the present, I'm busy reviewing my lessons in order to take the college entrance examination. I hope to go to Beijing University, that is one of the best universities not only in China but also in the world. I'll try my best to turn my dream to reality. Most of my classmates are also studying very hard to realize our wishes. I do believe everyone will be able to enter into a very good university and college. | 1. _____ 2. _____ 3. _____ 4. _____ 5. _____ 6. _____ 7. _____ 8. _____ 9. _____ 10. _____ |