题干

实验室用高锰酸钾制取氧气,简要分为以下几步:①装药品  ②检查装置的气密性  ③排水法收集气体④固定装置  ⑤加热  ⑥把导管从水槽中取出 ⑦停止加热.实验操作顺序正确的是(   )

A:②①③④⑤⑥⑦

B:③①②⑤④⑥⑦  

C:②①④⑤③⑥⑦

D:①④②③⑤⑦⑥

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答案(点此获取答案解析)

C

同类题5

根据短文内容的理解,选择正确答案。

    Papa, as a son of a dirt-poor farmer, left school early and went to work in a factory, for education was for the rich then. So, the world became his school. With great interest, he read everything he could lay his hands on, listened to the town elders and learned about the world beyond his tiny hometown. "There's so much to learn," he'd say. "Though we're born stupid, only the stupid remain that way. "He was determined that none of his children would be denied (拒绝) an education.

    Thus, Papa insisted that we learn at least one new thing each day. Though, as children, we thought this was crazy, it would never have occurred to us to deny Papa a request. And dinner time seemed perfect for sharing what we had learned. We would talk about the news of the day; no matter how insignificant, it was never taken lightly. Papa would listen carefully and was ready with some comment, always to the point.

    Then came the moment—the time to share the day's new learning.

    Papa, at the head of the table, would push back his chair and pour a glass of red wine, ready to listen.

    "Felice," he'd say, "tell me what you learned today."

    "I learned that the population of Nepal is ...."

    Silence.

    Papa was thinking about what was said, as if the salvation of the world would depend upon it. "The population of Nepal. Hmm. Well……" he'd say. "Get the map; let's see where Nepal is." And the whole family went on a search for Nepal.

    This same experience was repeated until each family member had a turn. Dinner ended only after we had a clear understanding of at least half a dozen such facts.

    As children, we thought very little about these educational wonders. Our family, however, was growing together, sharing experiences and participating in one another's education. And by looking at us, listening to us, respecting our input, affirming our value, giving us a sense of dignity, Papa was unquestionably our most influential teacher.

    Later during my training as a future teacher I studied with some of the most famous educators. They were imparting what Papa had known all along—the value of continual learning. His technique has served me well all my life. Not a single day has been wasted, though I can never tell when knowing the population of Nepal might prove useful.