Bats are the only “flying animals” in the world. They can't see very well. We often hear “as blind as a bat”. Yet they have no trouble flying on the darkest nights and finding their ways round. How can bats fly and see at night? They fly by radar(雷达).

The bat's radar system(系统) works the same way as the radar in ships and planes. As a bat flies through the air, it makes a sound. If the sound hits things, it will come back and the bat's ears will receive the message. In this way the bat is able to know where the things are. Bats go out for food at night. In the daytime they hang in some dark places. Some people think bats are bad animals. In fact they are useful animals.

    More and more people like bicycling and it is no surprise. It is fun, healthy and good for the environment(环境). Maybe that's why there are 1. 4 billion bicycles and only 400 million cars on roads worldwide today. Bikes can take you almost anywhere, and there is no oil cost!

    Get on a bicycle and ride around your neighborhood. You may discover something new all around you. Stopping and getting off a bike is easier than stopping and getting out of your car. You can bike to work and benefit(受益) from the enjoyable exercise without polluting the environment. You don't even have to ride all the way.

    Folding(可折叠的) bikes work well for people who ride the train. Just fold the bike and take it with you. You can do the same on an airplane. A folding bike can be packed in a suitcase. You can also take a common bike with you when you fly. But be sure to look for information by getting on airline websites. Not all airlines are bicycle-friendly to travelers.

    Health Benefits of Bicycling:

    It helps to prevent heart diseases.

    Bicycling helps to control(控制) your weight.

    A 15-minute bike ride to and from work three times a week burns off five kilos of fat in a year.

    Bicycling can improve your mood(心情).

    Exercise like bicycling has been shown to make people feel better, more relaxed and self-confident.

    Bicycling is healthier than driving.

    A city without cars would be very strange, right? But Venice is such a city.

    Venice is in the northeast of Italy. It wasn't built on land, like Beijing or Shanghai, but on more than 110 islands. Seawater is everywhere around the city.

    Even so, travel isn't difficult. The waterways have always been the best way to get around. There are 117 waterways and more than 400 bridges that can guide you where you want to go.  People in Venice move from place to place by boat.

    Water makes the city special, but it is also a big problem. Sometimes tourists will have such strange experiences. One moment they walk across the Rialto Bridge, and there's nothing special. But when they come back to the bridge an hour later, it's underwater and everyone is wearing rain shoes.

    Once, people used too much underground water. This made the city get lower little by little. Now the city has gone down by 23 centimeters. Another problem is the rising seawater. The temperature has risen over the years. This has made the ice of the Arctic Ocean (北冰洋) melt( 融化). Every year, high waters hit the city in autumn and winter. When a lot of water comes, more than half of the city is underwater.

    Scientists are trying different ways to stop the city from getting even lower. The Italian government has asked some of Italy's biggest companies to build the MOST project, which was planned to be build under the seawater to stop the rising water. Anyway, this project is helping solve the problem.

The end of the year is drawing near, and winter is in full activity. The season brings along with its strong winds and snow — an environment that's never comfortable to be in.

 This unpleasant and even frightening part of winter can be often seen in literature. In Shakespeare's King Lear (1606), the king has given away his kingdom and been driven out by his two ungrateful daughters. He is out in the winter cold, suffering (遭受痛苦) things that are usually saved for the poorest and most unlucky human beings.

The winter is bad enough for Lear, but being driven out by his family is worse. A song from another Shakespeare's play, As You Like It(1599), is fitting for this poor old man's situation: "Blow, blow, thou winter wind/Thou art not so unkind/As man's ingratitude (忘恩负义)". Here, winter is used to bring out the ugliness of inhumanity (无人性). There aren't many things that are worse than winter, according to Shakespeare.

Once winter became less of a danger to human beings, it became more positive in literary works. Since Charles Dickens, the representation of the season in literature often has something to do with happy Christmas celebrations.

The cold of the winter weather provides a contrast (对比) to the fun going on indoors.

Dickens' A Christmas Carol (1843) was the start of this, but Christmas is still a common, cheery element (元素) in stories that feature winter scenes today. Consider the joy felt by Harry Potter and his friends in J. K. Rowling's Harry Potter and the Philosopher's Stone (1997) as they sit down for their festive meal：

"Harry had never in all his life had such a Christmas dinner. A hundred fat, roast turkeys; mountains of roast and boiled potatoes; platters of chipolatas; tureens of buttered peas, silver boats of thick, rich gravy and cranberry sauce."

It is almost as much a pleasure to read about the meal as it might have been to eat it.

Although winter still isn't the most cheerful season in novels and poems, it's safe to say that writers have surely "warmed up" since Shakespeare's days.

We usually send and receive information through the movement of our bodies. Body language can show different feelings. We often use gestures(手势) or body movements to show and express our mind. For example, when someone is giving a talk, he or she may often use his or her hands to emphasize(强调) points.

The victory(胜利) sign, the OK sign, the goodbye wave and the blowing of a kiss are all popular gestures in America. However, most of these gestures are not accepted(接受) by people in other countries. For example, the OK gesture means acceptance in America, but it has other meanings in other countries. In France, it means worthlessness(无价值), while in Greece it is a sign of quite disrespect(不尊重).

There are some other differences in the non-verbal(非语言的) messages of people of different sexes(性别). In American culture, men usually sit or stand with their legs apart and hands outward, while women usually keep their legs together and their hands at their sides. Women sit quietly than men most of the time. Women are also better than men at expressing themselves using gestures.

In short, body language is simple and useful, so we should learn how to use it in our daily lives.