空气中的PM2.5因为粒径小，面积大，活性强，易附带有毒、有害物质，且在大气汇总停留时间长、输送距离远，因而对人体健康和大气环境质量的影响很大， 目前很多省、市均在积极采取措施降低PM2.5指数．小明在“关注雾霾”主题班会上，提出的下列治霾措施中，不合理的是（ ）

在锐角三角形ABC中，a，b，c分别为内角A，B，C的对边，若A=2B，给出下列命题：

①$\frac{\mathrm{\pi }}{6}$＜B＜$\frac{\mathrm{\pi }}{4}$；

②$\frac{a}{b}$∈（$\sqrt{2}$，$\sqrt{3}$；

③a²=b²+bc．

其中正确的个数是（　　）

佳佳在实验室进行“凸透镜成像规律”的探究

选出下列划线字读音与其他三项不同的一项（    ）

Thousands of years ago，human(人类)didn’t live in towns．Sometimes they would live in caves(洞穴)or build camps in the forest．
Only about thirty people1 in each camp．The men would go hunting while the woman and children2food from trees around the camp．All the food was 3 among people in the group．Every few weeks they moved to another place to find more food．It was a simple life，but people had to be 4 .They had to make everything that they needed，and they had to know a lot about plants and animals．
Nowadays most people live in towns and cities，and they work in offices and factories．Life is 5than in the old days．There are fewer 6，but there is less excitement．Some people go7  excitement  sailing round the world．climbing mountains，or exploring(探测)caves．
Most people look forward to the8,a time when they can enjoy a change from the normal life．For some this means going camping．But camping today is 9 from camping in the past．Gas cookers，ready-made food and air-beds mean people can camp much more10 than they did in the old times．