You're thirsty and you get yourself a glass of water. Do you ever1how old that water really is? The glass of water that you're2may have fallen from the sky as rain only last week. However, water itself has been around pretty much as3as the earth has! In fact, 4oceans, seas and rivers cover 70％of the earth, there is a 5 supply(供给)of water, which keeps on moving round the earth. This is6of what's known as the water cycle. The sun heats up water and it turns into clouds, which are7from water vapor(水蒸气).When the clouds become8, the water falls back onto the earth as rain. Of course, clean water is absolutely essential for good health. The amount of safe drinking water has gone up around the world, but9one billion humans are still in great need10clean, drinkable water.

    Hello, human friends. My name is Nick. I am a turtle (海龟). I have lived in the 1 for over half a century. In general, turtles can 2 to be more than 100 years old. 3many of my friends are now dying from one thing: plastic(塑料).

    Human beings use too 4 plastic. When you throw plastic away, it doesn't just disappear. Over 90 percent of the world's plastic doesn't get recycled(回收). A lot of plastic 5in the ocean. Most of my friends do not know the danger of plastic. They think it is 6. But in fact, plastic is 7. Around 30 percent of my friends have plastic in their body. I have plastic in my body, too. Plastic is also 8 other sea animals. Last month, one of my friends died after eating 80 plastic bags. I feel so 9 about it.

    My human friends, please 10 using too much plastic. Maybe one plastic bag or one coffee cup won't make a difference. But when seven billion people all start to use less plastic, it will make a big difference.

    Each one of us shares this planet with seven billion others. And we all need 1. People and products need to move from city to city and country to country. However, we all know 2 most cars, motorcycles, boats and planes cause air pollution. They are also 3.This is a serious problem in many cities.4 inventors are coming up with creative ideas to try to reduce the pollution and noise.

    In many cities around the world, motorcycles are very 5. Now Vietnam has around 33 million motorcycles and China has almost 120 million. Motorcycles are a faster and cheaper way to get around a city than 6. Yet air pollution is a growing problem. In large cities, people7it is difficult to breathe. To solve these problems, a US company designed an environmentally friendly motorcycle. It uses electricity as fuel (燃料). As a result, there is 8 pollution. It's also quiet and fast. This makes 9 a good choice for getting around a city.

    The Italian city of Venice is a city with only a few 10. There are no cars in the city center,11 cars, water taxis and buses carry people along the city's canals (运河). However, they cause pollution, 12 to the water. English engineers Dick and Jim designed a solar –powered(太阳能) water taxi. The water taxi 13 run for a day after being recharged(重新充电). Planes also cause air and noise pollution. Designing an environmentally friendly airplane is a real 14. Some airplane companies have 15 to solve the problems. Swiss engineers have gone one step further. They developed a solar airplane. This plane holds the world record for the longest solar-powered flight-1,541 kilometers from Arizona to Texas in America.