《红星照耀中国》始终是许多国家的畅销书，是真实描绘中国红色区域的第一本著作。它是通过一个外国人的所见所闻，客观地向全世界报道了共产党和红军的真实情况，使西方人第一次了解到***人的真实生活。

集合A={a，b，（a，b）}含有____ 个元素．

传说阿基米德有一天和亥尼洛国王聊天时曾说：“给我一个支点，我将能移动地球．”这种“玩笑”看似夸张，其实却包含这样一个重要的规律：利用某些机械可以挪动重物，改变用力方向，或者改变物体运动的速度．假如你能够施加一个100牛的力，且受力点沿力的方向以1米/秒的速度运动，那么，利用杠杆（不考虑杠杆的质量）让你把一个120000牛的重物抬起5厘米，需要花费的时间为（　　）

根据短文内容，选择最佳答案。   

D

    Some people learn a foreign language easily. Others may not. How can you help yourself learn English? I think there are two ways to make learning English a little easier and more interesting.

    First, you should build up confidence（自信）. If you believe that you can learn, you will learn. When you read or listen to something, you may not be able to understand（理解） it all. Don't worry. You can use a dictionary to help you. You can ask your teacher or friends to help you. Do not be afraid of making mistakes. You can learn from mistakes.

    Second, practise using English. For example, write a diary in English every day, and you'll be able to write better. Speak English whenever you can. You may practise with your friends after class. Then you'll be able to speak better.

    Remember the famous saying, "Practice makes perfect." The more you practise using English, the better you'll learn it.

   Miracles（奇迹）will happen if you don’t give up trying. Even if you have1 for one hundred times, you may succeed when you try for the 10lst time.
   When I was born, my doctor told my mother that there was something wrong with my2 .  They were too soft to be able to walk. Although the news was bad, my mother didn’t become 3. She didn’t believe what the doctor said 4started to look for other ways.
   My mother kept looking for other doctors for me, and finally she5 . The doctor and his team in the hospital did 6they could to help me. They also asked my parents to teach me to do some 7to help me walk. One day when my mother came to pick me 8  . I crawled(爬) towards her. She was so surprised and happy that she couldn’t believe9  eyes. Crawling was not walking, but it was a good 10 . Day by day, I could walk by myself.
   When I grew up, my mother 11  told me these stories. She said that if I thought of what she said whenever I met 12 , I could do anything successfully. I have been working hard and I have turned out to be a very 13 person.. I get best grades in school and I am a good dancer and swimmer. 14 my mother’s strong resolution, I live a happy life now. What the story tells us, as my mother always says, 15: Never give up.