名称 | 氢 | 氦 | 锂 | 铍 | 硼 | 碳 | 氮 | 氧 | 氟 | 氖 |
符号 | ||||||||||
名称 | 钠 | 镁 | 铝 | 硅 | 磷 | 硫 | 氯 | 氩 | 钾 | 钙 |
符号 |
名称 | 水 | 氮气 | 臭氧 |
符号 |
We live in a small town and almost everyone knows each other. It used to be very quiet. Nothing much ever happened around here. However, these days something unusual is (happen) in our town. Victor, a teacher at my school, is really nervous. When he was interviewed the town newspaper, he said, "Every night we hear strange noises outside (we) window. My wife thinks that it could be animal, but my friends and I think it must be teenagers having fun. My parents called the policemen, but they couldn't find anything strange. They think it might be the wind. I don't think so!"
Victor's next-door neighbor Helen is (worry), too. "At first, I thought that it might be a dog, but I couldn't see a dog or anything else, either. So I guess it can't be a dog. But then, what could it be?" One woman in the area (see) something running away, but it was dark so she is not sure." I think it was too big to be a dog," she said." Maybe it (be) a bear or a wolf."
Everyone in our town is feeling(easy), and everyone has his or her ideas. There must be something visiting the homes in our neighborhood,what is it? We have no idea. Most people hope that this animal person will simply go away, but I do not think that is going to happen. The noise-maker is having too much fun creating fear in the neighborhood.
①有利于节约资源,保护环境
②基于我国人口、资源、环境问题的现状
③体现了“看不见的手”在资源配置中的作用
④表明我国在解决资源问题上坚持“开源”与“节流”并举
根据有关信息,回答下列问题:
①若其不变长度为零,求b的值;
②若1≤b≤3,求其不变长度q的取值范围;
①NaNO2 ②Fe2+ ③KMnO4 ④ ⑤
若∠α=45°,则sinαcosα;若∠α<45°,则sinαcosα;若∠α>45°,则sinαcosα;
sin10°,cos30°,sin50°,cos70°.