某同学在查阅中美关系资料时发现了“小球转大球”这一说法，他理解小球是指美国乒乓球队应邀访华，却不知道“大球”指什么。请你为他指出(     )

    We all want to study well. But do you know how to1 better and make your study get a good result? We all know that Chinese students usually study hard for long hours. This is very good, but it doesn't2 a lot. If you want to study effectively, you must have enough sleep, enough food, enough rest and 3. Every day you need to go out for a walk or visit some friends or some places. It's good for your 4. When you return to your studies, your mind will be refreshed and you'll 5more and study better. Here take English learning as an example. First you make great progress and you feel6. Then your language study seems to stay the same and you may 7 it. This can last for days or even weeks,8 you needn't lose hope.

    At some time, your language study will not take9 big jump.10you get enough sleep, food, rest and exercise, studying English can be very effective and interesting.

    Don't drop it along the way. Learn slowly and you're sure to get a good result.

电视剧《闯关东》讲述的是从清末到九一八爆发前，一户山东人家为生活所迫而背井离乡到东北“闯关东”的故事。而在中国古代史上北方人口则大量向南迁移，它所带来最重要的结果是（   ）