题干

氯化钠是日常生活中非常重要的化合物之一,结合你掌握的化学知识,下列说法合理的是

A:锌粒与盐酸反应时,若加入适量氯化钠晶体,可明显加快反应速率

B:氯化钠中所含化学键为离子键,含离子键的化合物一定是离子化合物

C:标准状况下,氯化钠溶液呈中性,溶液的pH=7

D:氯化钠溶液导电是化学变化,而熔融态氯化钠导电是物理变化

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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。

    Lots of people give you advice on overcoming fear. ____ However, I want to tell you that a world without fear would be more dangerous, less rewarding. So we want to treat fear as a friend? Here are three reasons.

    ____ Think about it. Do you get more nervous when you meet the girl (or guy) of your dreams? Which is more fearful, talking to the boss of your company or to some of your friends? ____ If you didn't have fear to guide you, you might not know that! Not so bad, right?

    Next, fear encourages us to take action. Fear is a call to action. In the past, our ancestors didn't run away in fear when they saw a tiger running toward them but tried to kill it for food. Now, most of us don't face serious danger like hungry tigers every day, but we do face serious bosses or public speaking. So, what can we do? ____

    Lastly, fear lets you know you are alive. Why do we like roller coasters? ____ Same for horror movies.

    So fear can guide you towards what's important for you and encourage you to take action to improve. Don't we all need that kind of friend?

A. The first is that fear is an excellent guide to opportunity.

B. They frighten us in a mostly safe way.

C. Imagine what life would be like without fear.

D. Let fear provide us with the energy to do what needs to be done.

E. Fear is showing you what is important and what matters to you.

F. Don't fear to be wrong.

G. They say if you can overcome fear, you will be successful.