The crow （乌鸦） is an ordinary （普通的） bird. It is about twenty inches （英寸） long and black all over. Crows are dirty birds because they live on old bad food. Crows eat a lot of waste food. In this way they are more useful to us than any other bird. They clean up the dirty things in our streets. Crows are always hungry. They look for food all day long, and in the evening you can see them in large numbers flying back to their nests (窝) in the trees. They sleep there at night. Crows are much noisier than other birds. Very often a large number of crows will get together on one house and talk. Sometimes they talk together, and sometimes they do it by talking like human beings (人类). It is easy to tell from(区别) crows' sounds whether they are pleased or angry. Perhaps crows talk a lot because they are friendly birds. A pair of crows will live together all their lives, and if one of them dies, the other one becomes very sad and quiet for the rest of its life and sometimes it dies, too.

E

    The Earth is our home; we must take care of it. This means keeping the land, air and water clean. Pollution is a dirty word. To pollute means to make things unfit or unclean to use. Pollution comes in many ways. We see it, smell it, taste it and drink it. Pollution is beginning to threaten (威胁) our health, our happiness and our life. Man has been polluting the earth from the time he first made fire, washed his clothes in the river and threw his waste on the ground. When land was used up or water became dirty, men moved on to another place. At first, the problem was not so serious because there was plenty of clean air, land and water. There weren't so many people then and their wants were fewer. All the dirty things could be absorbed (吸收) by nature and soon covered over. But this is no longer true. The increase of population and the development of industry(工业)have changed that. Man is slowly poisoning (毒害) his environment. Through the use of poison, man has polluted the land, killing the animals. By putting dirty water and chemicals into rivers and lakes we have polluted our drinking water, killing the fish.

    Our increasing population is part of the problem. More people, more waste.

    Where is this all to end? Are we turning the world into a big rubbish dump (堆存处), or is there any hope that we can get rid of (摆脱, 除去) the pollution? Luckily, millions of people have been warned of the danger of pollution. Large numbers of people are now working hard to bring pollution under control.

    Many animals do strange things before an earthquake. This news may be important. Earthquakes can kill people and knock down homes. The animals may help to save lives.

    Some animals make a lot of noise before an earthquake. Farmers have told about this. Dogs that are usually quiet have started to bark (吠). Horses on farms have run around in circles. Mice have left their holes and run away. Cows have given less milk.

    In a town in Italy, cats raced down the street in a group. That happened only a few hours before an earthquake. In San Francisco, a man kept tiny pet frogs. One Sunday, the frogs jumped around more than ever. They made loud noises, like bigger frogs. That night, an earthquake struck the city.

    People want to know when an earthquake is coming. Then they could get away safely. Right now, there is no sure way to know ahead of time. Maybe the best idea is watching the animals.

    There is a lot of salt on the Earth, and it mixes very well with water.

There is some salt in all water. Water on the land runs into lakes and rivers. These rivers run into the seas and oceans. They carry a little salt with them. Some of the ocean water moves into the air and clouds. It evaporates. Salt cannot evaporate. It stays in the oceans.

    The water in the oceans has more salt than river water. There is about 3. 5% salt in the ocean water. Some seas have more salt than others.

    Some of the water leaves the lakes. It evaporates, but the salt cannot. These lakes are very salty. There are two famous lakes like this. They are the Dead Sea in the Middle East and the Great Salt Lake in Utah(犹他州）in the United States. They are much saltier than the Atlantic Ocean（大西洋）and the Pacific Ocean(太平洋）.

    The Earth is about 4, 600 million years old Man lives on the Earth for only 35, 000 years. But we change our Earth in many ways. Many things we do are good, but some are not good for the Earth.

    Water pollution

    A lot of people, birds and fish die each day because of water pollution. Factories pollute the water. As a result (因此), the water in many rivers and lakes is now very dirty.

    Air pollution

    In big cities, factories, cars and buses are the main causes of air pollution. Many people in cities now have health problems. For example, Mexico City used to be a beautiful sunny capital, but today there are many clouds in the sky. And many people get ill because of the polluted air.

    Soil (土壤) pollution

    In order to have a better harvest (收获), some of the farmers use chemicals too much in their fields. That's bad for the soil.

    Hope for the future

    These problems are very serious for our future, so all of us should do something to protect the environment. If we can stop pollution, our Earth will become more and more beautiful.

    Do you think the people who use smart phones all the time are relaxed? A research shows that too much smart phone use in spare time can make people more stressed out.

    So what can we do in order to really take advantage of our spare time? We have collected the following activities that also take a few hours to complete, but you'll improve your health in the process (过程).

    Whether you're at home or on holiday, it's important to disconnect from the Wi-Fi. Walking in nature can do good to your health. As a professional(职业的)traveler, Samantha Brown put it in a recent passage, "I put my map in my back pocket, put down my phones and take a good, long walk. Just walk around."

    Go to bed earlier. What can help improve your mood? Extra sleep, naturally. Getting the right amount of sleep is very important to our health and studies show that we don't get enough of it.

    Read a book. And let yourself get lost in a good story. Research shows that reading can reduce(减轻) stress, keep your brain sharp and can even help you sleep better. Everyone should spend at least 30 minutes reading every day.

    Putting pen to paper is a good exercise. Try writing down your thoughts. Writing has a lot of health advantages. Besides, writing down your thoughts may even help clear your mind.