Many cultures have different ideas about why people catch colds. For example in the United States, some people think that you can catch a cold if your feet get cold. So, mothers tell small children to wear warm boots in the winter. In other places, including parts of the Middle East, some people believe that strong winds cause colds. So, on trains and buses, people usually don't like to sit next to open windows. In parts of Europe, some people think that wearing wet clothes will give you a cold. They say that after you go swimming, you should quickly put on dry clothes. Today, scientists know that colds are caused by a virus（病毒）. But the old ideas are still very strong, and many people still follow them to avoid（避免）getting ill.

Birthdays are celebrated（庆祝）all over the world. Some ways to celebrate birthdays are rather similar from county to country：candles，cakes，and birthday wishes. But there are also different ways to celebrate birthdays. Here are a few：

Flying kites —a popular hobby

People have been making and flying kites for about 2,000 years. No one knows for sure who invented the kite. Some historians (历史学家) believe the ancient Chinese might start the kite flying 2,000 years ago. And now it is still a popular hobby in China, Japan, Korea and other countries of the Far East where beautifully decorated kites appear in different colors. In China, there is even a special Kites Day on which children and adults fly kites. In Japan, families fly fish kites on Children's Day, May 5th.

    Simple kites are made by crossing two sticks and covering them with paper or cloth. And then people put a string at the end.

    Kites are made in many different sizes, colors and shapes. A flat kite is the oldest and simplest type of kite. It flies because air flows over and under the kite's wings. The pressure under the wings helps the kite lift into the air.

    Today most people fly kites as a hobby. Kite festivals are organized in many parts of the world.

    In a map of the world you can easily find two big cities, London and New York. London is the biggest city in Europe. New York is the biggest city in America. The streets in London are crowded and there is one of the world's biggest underground railway systems(地铁系统) .The streets in New York are just as crowded as those in London. And the New York subway carries more people each day than the London underground. There are a lot of big stores in these two cities. But New York has more supermarkets than London.

    In London there are many palaces(宫殿) and churches, for example, St. Paul's. New York isn't as old as London, and it hasn't got many old buildings. But its skyscrapers(摩天大楼) are much bigger than the buildings in London.

    London has more parks than New York, But New York's Central Park is much bigger than the biggest park in London.