下列各实验中都用到了水，其中主要体现水发生化学变化的是（   ）

阅读下面两首唐诗，回答问题。

送李侍郎赴常州

贾至

雪晴云散北风寒，楚水吴山道路难。

今日送君须尽醉，明朝相忆路漫漫。

送柴侍御

王昌龄

流水通波接武冈，送君不觉有离伤。

青山一道同云雨，明月何曾是两乡。

中国科协宣布“全国优秀科技工作者”评选结果，钟南山等十位科技工作者获评“十佳全国优秀科技工作者”。他们用自己的实际行动承担起了时代赋予他们的历史责任，那么时代赋予当代青年的历史责任是（   ）

    Andy is 12 years old. He is one of my best f____. He is a top student in Class 6. But he doesn't have a good diet.

    Every morning, he doesn't eat breakfast. It isn't right. I think breakfast is very i____ for him. It helps him start the day w____. He has lots of snacks like chocolates, sweets every day. They make him fat. It's bad for his health. Andy shouldn't eat too many snacks any more. In vegetables and fruits there are many vitamins. But he h____ eating them. These days he doesn't feel good.

    I think he needs to c____ his diet. And he needs to exercise more. I'm sure he'll be better.