Zheng He was an amazing man. He was born in 1371. Ten years later, he was caught by the army of a rich young man called Zhu Di and made to work for him. Over time the rich man saw that Zheng He was very clever and strong and they became close friends. In 1403 Zhu Di became the king of China and he asked Zheng He to join his government.

    The king wanted to learn more about the world and show other countries his power. He ordered many new ships to be built and made Zheng He their leader. Between 1405 and 1433, Zheng He led some sea trips to different parts of the world. He certainly travelled to India, Africa and the Middle East. A few people think his ships have even reached South America and Australia.

    Each trip lasted more than one year and it is believed he sailed more than 50,000 kilometres during the years of his travels. Zheng He led a fleet with about 28, 000 men and over 250 ships, such as boats for food, water and even soldiers horses.

    On these trips he took many Chinese goods like silk and medicine with him to give to foreign kings or to sell for local goods. He returned from each trip with boats which were filled with expensive things such as gold and treasures, foreign guests and strange animals like a giraffe.

    It is a pity that we may never learn everything about Zheng He's travels. The Columbus of the East, Zheng He, died in 1433. After that. The new king had these trips stopped and he burned almost all the books about Zheng He's travels, because he believed the trips were unlucky and too expensive. It is only in the last 50 years that historians have begun to carefully study the adventures of great Zheng He.

Boys and girls, let's do an experiment in today's lesson. 

Things you need to prepare: 

Instructions: 

1) Fill the glass or jug about 2/3 full with water. 

2) Drop the egg carefully into the glass and watch it going down towards the bottom. 

3) Take the egg out and add about 5 spoons of salt. Test to see if your egg goes up. 

4) Add more salt if the egg is still at the bottom. 

The science behind it: 

Things go down in the water when they are denser (密度更大的) than the water. By adding salt we make the water denser. Once the water is denser than the egg, it goes up. 

You can also try other things to see if you can have the same result. 

Example in daily life: 

The Dead Sea is the lowest sea in the world. The Dead Sea has a high concentration (浓度) of salt. So there is nothing living in the Dead Sea. As the experiment above, people can also float (漂) in it. But it is not good to float for a long time.

Nigeria is a hot and dry country in Africa where electricity is not available to many homes. Most people grow and sell their own fruit and vegetables. Keeping them fresh in the hot place is a real challenge. Without a fridge, most fresh food goes bad in a couple of days. Throwing away the food means losing money for poor families. Eating the bad food causes serious health problems. 

Local teacher Mohammed Bah Abba was worried about this problem and decided to solve it. As a boy born into a family of clay pot（陶罐）makers, Mohammed knew that these traditional clay pots could keep water even when dry. In the 1990s he used this traditional knowledge and his understanding of science to invent a cooling system（冷却系统）. It worked as a"desert fridge". 

Mohammed's cooling system is made up of two pots —a small pot inside a larger pot. In the space between the two clay pots, there is wet sand. People put the fruit and vegetables in the smaller pot, and cover it with a wet cloth（布）. Then they leave the larger pot in a dry place. When water from the sand evaporates（蒸发）, it causes the temperature in the pots to go down. This way the food in the smaller pot is cool. 

With the pot-in-pot cooling system, food stays fresh much longer. Mohammed's "desert fridge" has improved the lives of thousands of people. So in 2001 he won the Rolex Award for Enterprise, which is for the people who try to make the world a better place. 

要求：（1）要点齐全，语法正确，逻辑通顺，语句优美，60词左右。（2）文中不得出现真实人名和校名。

I'm a student in No.2 middle school. I want 1 you something about my new classroom. It is nice 2 clean. What's in the classroom? Look, a long blackboard and a flag 3 in the front of the classroom. 4 flag is red and I think it's very beautiful. There are thirty-eight small desks and 5 . This is a teacher's desk. A computer is on the big desk. Teachers use it to give us classes. We can also use it for study.

Let's look at the back wall. You can see 6 beautiful photos. We took them together. Our teacher puts them 7 the wall so everyone can see them. What is this on the floor? Oh, it's our volleyball. Most of the students like 8 volleyball in our class and we are good at it. Every Friday afternoon, we play it 9 on the sports field. We 10 a volleyball game at school next week. I think my classroom is great! Do you like my classroom?