题干

通过复习总结,你认为下列对化学知识概括合理的组合是    (    )
①能与酸反应的氧化物,一定是碱性氧化物
②原子晶体、金属晶体、分子晶体中都一定存在化学键
③原子晶体熔点不一定比金属晶体高
④在熔化状态和水溶液中均不能导电的物质称为非电解质
⑤NF3的沸点比NH3的沸点低是因为N-F比N-H键的键能大
⑥过氧化氢和液氮的分子中都有非极性共价键

A:只有①②⑥

B:只有③④

C:只有③⑥

D:只有⑤⑥

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答案(点此获取答案解析)

C

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    One October morning, I got off the all-night train in Mandalay, a city in Myanmar. A rough man came up and offered to show me around. The price he asked was less than I would pay for a bar of chocolate at home. So I climbed into his trishaw(三轮车).

    As he was showing me around, he told me how he had come to the city from his village. He'd earned a degree in mathematics. His dream was to be a teacher. But of course, life is hard here, and so for now, this was the only way he could make a living. Many nights, he told me, he actually slept in his trishaw so he could catch the first visitors off the all-night train.

    And very soon, we found that in certain ways, we had so much in common---we were both in our 20s, we were both fascinated by foreign cultures----that he invited me home.

    So we turned off the wide, crowded streets, and came to rough, wild alleyways(小巷). I really lost my sense of where I was, and realized that I could easily get cheated or something even worse.

    Finally, he stopped and led me into a hut. And then he reached under his bed. Something in me froze. I waited to see what he would pull out. And finally he took out a box. Inside it was every single letter he had ever received from visitors from abroad.

    So when we said goodbye that night, I realized he had also shown me the secret point of travel, which is to go inwardly(向内心)as well as outwardly to places you would never go otherwise, to go into uncertainty, even fear.

    At home, its dangerously easy to think we're on top of things. Out in the world, you are reminded every moment that you're not, and you can't get to the bottom of things, either.