In the 13th century, the famous Italian traveler, Marco Polo, traveled a long way to China. During his stay in China, he discovered that the Chinese used paper money. In western countries, people did not use paper money until the 15th century.

A Chinese man called Cai Lun invented paper almost 2000 years ago. He made it from wood. Now paper still comes from trees. We use a lot of paper every day. Every day, people throw away about 280 tons of paper in our city. It takes 17 trees to make one ton of paper. This means that we are cutting nearly 4800 trees every day. Since it takes more than 10 years for a tree to grow, we must start using less paper now. If we don’t, we will not have enough time to grow more trees to take the place of those we use for paper.

So how can we save paper? We can use both sides of every piece of paper, especially when we are making notes. We can choose drinks in bottles instead of those in paper packets. We also use cotton handkerchiefs and not paper ones. When we go shopping, we can use fewer paper bags. If the shop assistant does give us a paper bag, we can save it and reuse it later.

As is known to all, the earth is having trouble burdening so large a population. Will we have another place to live and work in the future? Maybe on Mars (火星)? Many scientists think so. In fact, they are already working on plans to turn Mars into a new Earth.

Humans need three basic things to live: water to drink, air to ①         and food to eat. Because of the shortage of those above, it is impossible to live on Mars right now. Then how can we make Mars a right place for humans to live on? The answer is to change its environment similar to Earth’s.

On Mars, the ②         is about -60℃. So one of the main purposes is to warm it up. One idea for warming Mars comes from a problem here on the Earth——climate change. Most scientists agree that Earth is becoming warmer because of increased levels of greenhouse gases (温室效应气体) in our atmosphere. We might create similar conditions on Mars by building factories that give off greenhouse gases. The gas will change the atmosphere on Mars. Rain will fall, and it may be possible to grow plants for food. There will be many difficulties ③          changing Mars. The program could take many centuries, and the cost will be high. We have some of the technology, such as the ability to create greenhouse gases, but not the money. Anyway, living on Mars is a real possibility for future people.

A cup of tea is almost a symbol（象征）of British culture. British people were very interested in a hot drink, especially if it is served with some cakes or biscuits. Here are some facts about tea drinking habits in Britain.

There is no real tea time.

All around the world, everyone thinks that British people drink tea every day at 5 o’clock in the afternoon. In fact, we drink tea at every hour of the day, from the minute we get up to the last thing before going to bed. Of course it’s possible that a British person will drink tea around the middle of the afternoon, but it’s also common to drink it with breakfast.

The perfect partner

Scones（司康饼）are a simple kind of cake, a little sweet and usually served with jam（果酱）and cream. They are excellent with tea. In the daily life, if you order a “cream tea” in Britain, you will get a teapot（茶壶）with a plate of scones.

Milk in tea

British people nearly always put milk in their tea. This seems strange to people from other European countries. They would rather drink their tea without adding anything to it. In Britain, people add a certain number of milk depending on taste, so the tea doesn’t look clear enough.

People are always surprised when I say that I prefer coffee to tea as a British person. Tea really is part of our culture, whether we like it or not!