位于亚洲与欧洲分界线上的是（     ）

纷繁的世界，多彩的生活，我们拥有一个共同的名字——“公民”。在社会生活这个大舞台中，每个公民都扮演着各种角色，如：子女、家长、教师、学生等。亲爱的同学们，你知道吗？每当我们扮演这些角色的时候，都享有宪法和法律赋予我们的权利，同时也必须履行相应的义务，只有这样才能扮演好这些角色。 

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   If you think English means endless new words, difficult grammar and sometimes strange pronunciation, you are wrong. Haven’t you noticed that you have become smarter since you started to learn a language?
   According to a new study by a British university, learning a second language can lead to an increase in your brain power. Researchers found that learning other languages changes grey matter. This is the area of the brain which processes information. It is similar to the way that exercise builds muscles.
   The researchers also found the effect is greater on the younger people who learn a second language.
   A team led by Dr. Andrea Mechelli, from University College London, took a group of Britons who only spoke English. They were compared with a group of “early bilinguals(通两种语言的人)”, who had learnt a second language before the age of five, as well as a number of later learners.
   Scans showed that grey matter density（密度）in the brain was greater in bilinguals than in people without___________________. But the longer a person waited before mastering a new language, the smaller the difference was.
   “Our findings suggest that the structure of the brain is changed by the experience of learning a second language,” said the scientists.
It means that the change itself increases the ability to learn.
   Professor Dylan Vaughan Jones of the University of Wales, has researched the link between bilingualism and maths skills. Having two languages gives you two windows on the world and makes the brain more flexible,” he said, “You are actually going beyond language and have a better understanding of different ideas.”