题干

化学学科的思维方法有多种,其中推理是常用的思维方法.以下推理正确的是(   )

A:中和反应生成盐和水,所以生成盐和水的反应一定是中和反应

B:活泼金属与稀盐酸反应放出气体,能与稀盐酸反应放出气体的物质一定是活泼金属

C:燃烧一般都伴随发光、发热现象,但是有发光、发热现象的不一定是燃烧

D:碱的溶液都能使酚酞试液变红,所以能使酚酞试液变红的一定是碱的溶液

上一题 下一题 0.0难度 选择题 更新时间:2018-10-20 10:38:38

答案(点此获取答案解析)

C

同类题3

阅读理解

    One afternoon last week, I saw three tearful children from my son's school being comforted by teachers. That morning, my 11-year-old had stomach pains, retching(干呕)into a bowl. Talking to other mothers later, I heard about other children with stomachache or difficulty sleeping the night before.

What caused so much pain? Sports day. Sports day might be necessary at a highly-competitive independent school, but not at a village primary school. For the children who can fly like the wind, sports day causes no problem. For those who are overweight or just not good at sport, it is a nightmare(噩梦). Even for those who enjoy running but fall halfway down the track in front of the entire school and their parents, it can prove a disaster.

    Why do we put our children through this annual suffering? Some may say competition is character building; or it's taking part, not winning, that's important; or that it is a tradition of school life. I just felt great pity for those children in tears or in pain.

    Team games at the end of sports day produced some close races, wild enthusiasm, lots of shouting—and were fun to watch. More importantly, the children who were not so fast or quick at passing the ball were hidden a little from everyone's eyes. Some of them also had the thrill of being on the winning side.

    I wish that sports day could be abandoned and replaced with some other less-competitive event. Perhaps an afternoon of team games, with a few races for those who want them, would be less stressful for the children and a lot more fun to watch.