问题
选择题
下列气体中既能燃烧又能使金属氧化物还原的是
A.氧气
B.一氧化碳
C.二氧化碳
D.甲烷
答案
答案:B
题目分析:能燃烧又能使金属氧化物还原,那就说明该气体的化学性质既有可燃性又有还原性,而既有可燃性又有还原性的物质在初中阶段有三种物质:碳单质,氢气,一氧化碳,A、氧气具有助燃性,不具有可燃性,C、二氧化碳既不燃烧也不支持燃烧,D、甲烷虽然具有可燃性,但没有还原性,故选B
下列气体中既能燃烧又能使金属氧化物还原的是
A.氧气
B.一氧化碳
C.二氧化碳
D.甲烷
答案:B
题目分析:能燃烧又能使金属氧化物还原,那就说明该气体的化学性质既有可燃性又有还原性,而既有可燃性又有还原性的物质在初中阶段有三种物质:碳单质,氢气,一氧化碳,A、氧气具有助燃性,不具有可燃性,C、二氧化碳既不燃烧也不支持燃烧,D、甲烷虽然具有可燃性,但没有还原性,故选B
My oldest child, Emma, just returned to campus after a long holiday break to finish up her last period of ______. These days, friends and family have begun _____ me with one question: What is she going to do after _____? The job market is, after all, awfully ______. Just this month the Federal Reserve Bank _____ a study showing that “recent graduates are ______ working in low-paid jobs or working part-time.” The ______ spot, according to the study, is for students who majored(主修) in STEM— science, technology, engineering and ______— areas in which recent graduates “have______ to do relatively well”. But Emma is a student of the humanities(人文) at a small college. She’s an American Studies major with a(an) ______ on the politics and culture of food. For quite a while, I think her field of study is so fashionable right now that I’m not the least bit ______ she will find a good job. Yet the more I’ve thought about it, the more I’ve decided to be honest. “I’m not sure what Emma is going to do,” I now say. “But she’s gotten a great education and has really found her ______. — and I know those things will serve her well over the _____ of her life.” Nowadays, more and more universities and colleges are being ______ by the salaries of their recent graduates. In this climate, ______ your kid to study the humanities, seems, at best, unwise or, at worst, unconcerned with ______ a living. But a college is not a vocational(职业) school. And promoting STEM subjects should not be society’s only answer to helping the next generation grow in a competitive world. From the beginning, we never urged Emma to ______ a college or a major with an eye on its expected return on money, ______ more and more families are doing. To Emma, what really ______ will be something that we may not be able to measure for quite a long time: Emma’s ______ to the world and how happy she is in it.
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