题干

将铁丝放在空气中无论怎样加热,铁丝只是发红,不会燃烧,而将烧红的铁丝放在盛氧气的集气瓶内,它就会火星四射,剧烈燃烧,下列解释正确的是(   )

A:因为铁丝放在空气中不会达到它的着火点

B:因为空气中含有灭火剂二氧化碳

C:铁丝的着火点太高

D:集气瓶内氧气浓度大,扩大了铁丝与氧气的接触面积;同一时刻,一定的空间内,铁丝与氧气分子碰撞的次数大大地增多,使燃烧反应能剧烈地发生

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D

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    I recently posted a picture on Facebook from the movie Mad Max, a film where two groups race through the desert in steampunk vehicles, and wrote, “Actual picture of my way to work today.” It was meant to be a joke because of the sandstorms in Beijing, but one of my friends from back home thought it was real.

    I couldn't imagine how they could think that is actually what China is like. China has so many more conveniences and advantages than the West, and many of my friends agree. “I don't know how I will be able to deal when I go back home,” said a friend who is about to end her gap year in Beijing. “I've become so spoiled in China.”

    China seems to be leading the way in innovation(创新) and convenience for daily life. Back home I could never shop, pull out my phone and scan a QR code to pay.

    There have been rumors of starting bike sharing in my hometown for years with little success while bike sharing suddenly appeared in Beijing overnight. I just step outside and scan a code, and I am on my way.

    Going out to eat with a group of friends back home was troublesome for both the group and the servers. Splitting bills and swiping(刷) 10 different cards or making change for each person in the group can be a pain. But with China's WeChat, you can quickly send your friends your part of the bill.

    The list goes on…

    When I first arrived in Beijing, I was dead set on leaving in a month. That month has come and gone. Now, when someone asks me when I'm coming back, I think to myself, “Who knows?”

    While my friends think I am riding through the desert on a motorbike, I am actually taking a Didi for what is the equivalent of $5 in the US.

    With all the conveniences and technology here, I may never want to go back.