题干

A、B、C、D、E是初中化学常见的5种化合物,均由碳、氢、氧、氯、钠、钙6种元素中的2种或3种组成,常温下它们的转化关系如下图所示(部分反应的生成物未全部标出),下列推断正确的是(   )

A:若E是CO2,A一定是Na2CO3

B:若E是HCl,A一定是CO2

C:若E是NaOH,B一定是酸

D:若E是Na2CO3,B一定是酸

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C,D

同类题4

根据首字母提示确定需要填写的单词

    We usually have three meals a day, breakfast, lunch and supper. Which meal will

    c____ us the fewest health problems if we have to miss one ? Most people would rather not have breakfast, especially teenagers. They just eat some snacks or fast food i____. What will happen if we do like this?

    Many scientists and doctors in the field of health consider breakfast to be the m____ important meal of the day. If we eat a good breakfast, they say, we will have e____ energy we need to begin our working day. They remind us that our bodies burn the energy from food within four hours. A____ we may use up less energy while we sleep, it's a long time until morning and we still wake up with the need for a lot more fuel.

    One recent study c____ out in the USA tested a large number of people from 12 to 83 years old. These people were given different kinds of breakfasts, and sometimes, some of them didn't eat breakfast completely. The r____ showed that if a person eats an adequate (充足的) breakfast, he or she will work more actively than that who eats a very poor breakfast or doesn't eat breakfast. It also showed that children don't do well if they go to school w____ eating breakfast. They can't focus on their lessons for a long p____ of time when their stomachs are making some noise. In addition, the study suggested that avoiding breakfast may i____ the chance of a heart attack.

    To sum up, none of the three meals can be missed. We should find time to make proper meals and then enjoy them.