Challenges
For thousands of years, people have accepted challenges in different fields. There are not only physical challenges, but also social and intellectual challenges. Some people risk their lives in playing sports to see how well they can do. Others try to make and invent something to make life easier. Whatever they are, people enjoy challenges.
Why do people enjoy these challenges? There are probably many reasons. One is curiosity. The other is the personal feeling of success, of achievement. And nowadays, for some people, it is a business.
Today we still have many challenges before us. Medical science faces the challenges of conquering many diseases that still attack human beings. Engineers and planners must build new cities and design and produce new kinds of transportation. Scientists must develop new forms of energy. In short, we live in an age of challenges.
第一段写有多种多样的挑战，人们愿意接受挑战people enjoy challengex；第二段写人们为什么愿意接受挑战why people emjoy challenges，主要有两个原因；第三段写今天仍有许多领域的问题有待探索。
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