题干

 人类对原子结构的认识始于对静电现象的研究,下列有关说法中正确的是(  )

A:摩擦起电创造了电荷

B:自然界只存在正、负两种电荷

C:同种电荷相吸引,异种电荷相排斥

D:从静电现象认识到原子核是可分的

上一题 下一题 0.0难度 选择题 更新时间:2019-03-26 04:59:44

答案(点此获取答案解析)

B

同类题2

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    As we all know, sleep is very important and necessary. I would love everyone to develop the following four habits to have better sleep without needing the alarm(闹钟)wake-up call.

    ____If you eat much food an hour before you go to bed, your body will hate you, because your body needs time to digest while you are still awake.

    ____When I hear on TV that people just need 30-minute exercise a week, I think that's wrong. Every person should get 30-minute exercise every day. When you exercise, your body uses energy and feels tired. You have to recover from the tiredness. ____ The harder you exercise your body, the faster it falls to sleep and the better it sleeps.

    Turn the TV off. There are a few shows I still watch, but they will never get in my way of (妨碍) sleep. The bedroom is only for sleeping and rest. ____.

    ____A question to ask yourself: If I didn't have an alarm, what time would I get up? If that time is the time you need to get up, you should probably throw away the alarm. If the time you actually get up is much later than the time you need to get up, make great changes to your way of life and the time you go to sleep. No one should need an alarm.

A. Exercise for at least 30 minutes every day.

B. Don't eat any food 4 hours before you sleep.

C. Throw away the alarm.

D. Sleep is one of the most important things in our lives.

E. Your body recovers when you are sleeping.

F. Try to get up as early as you can.

G. Take the TV out of your bedroom.