下列过程发生化学变化的是
A．酒香扑鼻
B．火药爆炸
C．干冰升华
D．用金刚石切割玻璃
答案：B
题目分析：物理变化和化学变化的根本区别在于是否有新物质生成，如果有新物质生成，则属于化学变化；反之，则是物理变化。A、酒香扑鼻是分子的运动，没有生成了新物质，属于物理变化，B、火药爆炸是火药在有限空间急速燃烧引起，有生成了新物质，属于化学变化，C、干冰升华式由固态变为气态的过程，没有生成了新物质，属于物理变化，D、用金刚石切割玻璃是物质形状的改变，没有生成了新物质，属于物理变化，故选B
During my second year of middle school, our teacher gave us a test. I studied hard and __46 well in all the subjects, so the questions were not difficult for me. 47 I stopped when I read the last one：“What is the 48 of the woman that cleans the school?” Of course this was a joke. I saw the cleaning woman every day. She was short and about 60 years old. She had dark hair. But 49 would I know her name? I had never talked __50 her before. In fact, I had never even thought about talking to her. I started to feel rather guilty(惭愧的).Finally, I 51 my paper, without finishing the last question. Before the class ended, one student asked, “Will be last question count(计入) toward __52 grade?” “Of course,” the teacher said, “In your life, you will meet many people. All are important. They deserve(值得) your attention and care, even if you just 53 and say hello to them.” I’ve never forgotten that 54 _. I should get to know all of the people who work and live around me. That was, perhaps, the most 55 lesson of my life. Later, I learned that the cleaning woman’s name was Dorothy.
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