Taking away a city's rubbish is a big job. Every day tracks come into a city to collect it. Most rubbish is made up of things we can't eat or use. If we kept these things we would soon have a mountain of rubbish.

    In some cities the rubbish is collected and taken outside of city to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system. The sewage system takes away the used water from toilets, bathtubs and other places.

    To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbish-filled land. Finally, a house or a school may be built there, and then you'd never know that this had once been an old rubbish dump.

    In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly change into something called humus, which looks like black earth. It is rich with the kinds of things that feed plants and help make them grow.

    Animals are natural resources that people have wasted all through our history. Animals have been killed for their fur and feathers, for food, for sports, and simply because they were in the way. Thousands of kinds of animals have disappeared from the Earth forever. Hundreds of animals are on the danger list today. About 170 kinds in the United States alone are considered in danger. Why should people care? Because we need animals, and because once they are gone, there will never be any more. Animals are more than just beautiful or interesting. They are more than just a source of food. Every animal has its place in the balance of nature. Destroying one kind of animal can create many problems. For example, when farmers killed large numbers of hawks, the farmers' stores of corn and grain were destroyed by rats and mice. Why? Because hawks eat rats and mice, with no hawks to keep down their numbers, the rats and mice multiplied quickly.

    Luckily, some people are working to help save the animals. Some groups raise money to let people know about the problem. And they try to get the governments to pass laws protecting animals in danger. Quite a few countries have passed laws. These laws forbid the killing of any animal or plant on the danger list. Slowly, the number of some animals in danger is growing.

You may have seen such a photo: with a long white beard(胡须) and wearing a bamboo hat, an old fisherman stands on a boat. Huang Quande looked like this when tourists took photos with him on the Lijiang River in Guilin, Guangxi. He became famous on the internet that many believed the fisherman on the back of the 20-yuan Renminbi banknote(纸币) was based on his image(形象). Sadly, Huang passed away at the age of 94 on Feb. 18.

According to Jimu News, Huang shows the true spirit of the Lijiang River. He was a positive(乐观的) and kind man. In his 90s, Huang could still move his boat with speed. After he gave up fishing and became a photo model in 2008, he took photos with tourists world wild. 

The image of the fisherman on the back of the 20-yuan Renminbi banknote is not just about one man. Instead, it is a cultural symbol that makes the Guilin landscape(风景)what it is. 

In fact, the different backsides of the fifth series of Renminbi banknotes show the most iconic(标志性的)landscapes in the country. Each of them carries its own cultural value. 

For example, on the back of the 5-yuan banknote is Taishan Mountain in Shandong-For thousands of years, many emperors would go there and pray(祈祷)for the country's prosperity繁 荣). On the back of the l-yuan banknote are the Three Pools Mirroring the Moon(三潭映月)in West Lake, Zhejiang. Since ancient times, it has been a great place for moon watchers during Mid-Autumn Festival. The candle lights from the three pagodas(塔) are reflected on the water and look like little moons.
 

The Renminbi pictures have helped make  the landscapes even more popular among  tourists. Following the banknotes from 1 yuan  20yuan Lijiang River, Guangxi to 100, Pan Jinyu from Chongqing had a "banknote tour" when he was 21. "I want to finish a ceremonial(有仪式感的) journey and feel the beauty of our country. "he said. 

Our schooldays are the best and happiest days in our life. We should learn not to waste this wonderful time. 

Be positive (积极的). Don't say things are difficult or boring. We should be interested in the school life and school subjects, such as Chinese, maths and so on. We should join in lots of activities. We will enjoy ourselves very much. If we want to have a rest from schoolwork, we can go to some public places to do volunteer work (义工). 

Keep healthy. We need to have a good breakfast so that we won't be hungry in class. If we go to bed late, play the phone until (直到) midnight and don't get enough sleep, we will feel sleepy in class. In order to keep our body healthy, we should also do some sports. 

Study hard right now. Some students always say that they will study hard tomorrow. It is important to study today and the following every day. Everyone wants to be the first one to get to the top of mountain. In fact, if we fall behind, it will be very difficult for us to catch up (赶上). 

Don't be too disappointed (失望) if things sometimes go badly wrong. We should always believe that we are the best. 

Here are some greeting customs (打招呼习俗) in different cultures. 

French people greet each other with a handshake, but close friends kiss each other on both cheeks (脸颊) when they first meet and before they leave each other. In South Korea, it is better for people to bow when greeting each other. A bow is followed by a handshake. While shaking someone's hand, it is polite to support the right forearm (前臂) with the left hand. Kissing on the cheek is a common way of greeting in Brazil. But in a formal situation, people often shake hands. Men should shake hands before and after meeting each other, and if they become friends with each other, a light hug is often given. In a social situation, it's polite to greet everyone in the room in Ghana. A handshake is used in greeting, and the palm (手掌) must directly touch the palm of others'. People think it's impolite to touch the back of the hand.