题干

在化学世界里没有生命的阿拉伯数字也变得鲜活起来,它们在不同的位置表示着不同的含义.下列化学符号中数字“2”表示的意义正确的是(   )

A:Mg2+:一个镁离子带2个单位正电荷

B:CO2:二氧化碳分子中含有氧原子

C:2H:2个氢元素

D:CaO+2 :氧化钙的化合价为+2价

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A

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(Q = Question; A = Answer)

    Situation I

    Q: If someone sits right next to me in an empty movie theater, is it rude to move?

    A: Maybe, but nobody will fault you for it. Chances are that close sitter doesn't realize he disturbs you, so he may miss your annoyance. You undoubtedly aren't the first person he's met who needs enough room. Forgive his bad judgment, move quietly and enjoy the show.

    Situation II

    Q: If I use the bathroom at a store, do I need to buy something?

    A: Consider frequency and urgency. Is this a one-time or an emergency? If so, you don't have to buy anything, but it would be kind if you did. However, if you regularly use the bathroom at this place, then you are a customer, and you should act like one.

    Situation III

    Q: If someone is talking loudly on the bus, is there a nice way to ask him to keep it down?

    A: No. Try other means.1) Stare at him until he gets aware of it and quiets down. 2) Lift your finger in a silence motion(动作)and smile. 3) Put on earphones and ignore him.

    Situation IV

    Q: If I remember my friend's birthday a day late, should I apologize or just wish her a happy birthday like nothing happened?

    A: This is the reason why the word belated was invented. "Happy belated birthday!" is short for: "Well, I know I forgot, but then I remembered. Forgive me and happy birthday."

    Situation V

    Q: Can I lie about seeing a text because I was too busy or lazy to respond(回复) to it?

    A: Don't lie. Receiving a text does not mean you need to respond to it. Why waste a perfectly good lie when the truth will serve? "Yes," you can say if ever asked, "I saw it." No explanation is needed as to why you don't respond.