由三个大洲（亚、欧、北美洲）包围的大洋是（    ）

甲同学方案：合金粉末 过滤，将得到固体洗涤、干燥、称量，称得质量为a克．

乙同学方案：合金粉末 过滤，将得到的固体洗涤、干燥、称量，称得质量为b克．

请回答下列问题：

已知点M在平面ABC内，并且对空间任一点O，$\overrightarrow{OM}$=x$\overrightarrow{OA}$+$\frac{1}{2}$$\overrightarrow{OB}$+$\frac{1}{3}$$\overrightarrow{OC}$则x的值为（　　）

    Every school has its own rules. How many1are there in your school？ At some schools, the students 2 to wear uniforms on school days. But many students don't like to wear uniforms. They think the uniforms are the ugliest 3 in the world. But the school don't allow students to wear 4 own clothes at school. So some students draw cartoons or some famous singers on their 5. They think it is very6that everyone wears the same. It is very unfair(不公平的） that teachers and students are wearing7. But most of the students 8the rules. What do you think 9 it? Do you 10your school uniforms?

下图是“2008年某城市新区规划图”。针对规划实施中出现的问题，2015年对原规划进行了修编。右下图为“2015年修编后的该市新区规划图”。读图，回答下列各题。