题干

锂电池是一种新型的高能电池,质量轻、电容量大,颇受手机、电脑等用户的青睐.某种锂电池的总反应式可表示为:Li十MnO2=LiMnO2,下列说法正确的是(   )

A:该反应中锂元素的化合价发生了改变

B:该反应中MnO2是催化剂

C:LiMnO2属于氧化物

D:锂电池放电时把电能转化为化学能

上一题 下一题 0.0难度 选择题 更新时间:2019-09-07 06:39:19

答案(点此获取答案解析)

A

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    Tim Becker and his neighbors are doing something to make their neighborhood a safe area.

    When Tim Becker gets in his car to go shopping, he doesn't1 drive to a store and back home. He always looks 2up and down the streets of his neighborhood. He looks for anything 3 such as strange cars, loud noises, 4 windows, or people gathering on street corners.

    Tim 5 to a neighborhood watch group(巡逻小组)in Strongsville, Indiana, USA. The neighborhood watch group6 on his third Wednesday of every month. That's 7 Tim gets together with about ten of his neighbors to discuss community 8 Members of the neighborhood watch group want to help the police 9 their homes, streets, and families.

    Tina Stedman,10president of neighborhood watch group, agrees with Tim. “People seem to think that crime happens to other people but not 11them. Actually, it really happens,” she said, “and I think nobody has the12 to steal from other people or to make them feel 13 at their own homes.”

    Alex, a member of the group, said that all the neighbors were14to help one another, “We15 each other's homes. We keep watch on the neighborhood at night and on weekends. Usually a16 of four or five of us goes out together. If something doesn't look right, we will call the 17 For example, if we notice a group of teenagers who seem to be looking for 18 or someone destroying property(财产), we report to the police.”

    Alex feels the neighborhood watch group19a lot in reducing crimes. Her husband Jim agrees, “Police are good people, but they can't do20.