Steel, concrete(混凝土) and glass are the usual materials in any skyscraper. But more high buildings are now using wood.

    In the last four years, Australia, Norway, England and Canada have all built wooden skyscrapers. The latest one is in Sweden, a new, 19-storey wooden hotel called "Sida vid Sida" (Side by Side).

    Why are wooden skyscrapers being chosen ahead of concrete ones? Let's find out.

    Is it strong enough?

    Wood has been used in many Chinese buildings for thousands of years, but is it strong enough for skyscrapers?

    "There's a lot of new materials made out of wood that are able to build big buildings," material expert Dr Michael Ramage told CNN when he was interviewed.

Architects (建筑师)have done thousands of experiment to make sure it is. They place layers of wood across one another coated with special glue to create very strong material.

Wood also lasts a long time and doesn't break down if it is well looked after. The examples include the rooftops of Beijing's Forbidden City and some 700-year-old houses in England.

Ramage also said on the internet that bamboo could be cut in special ways to make it even stronger than normal wood.

    Won't it catch fire?

    Wooden buildings sound dangerous when it comes to fire. But experts say they may be safer than concrete ones if there is a fire.

    "Wood doesn't burn in the way the public imagines," Ramage said. Very small pieces of wood catch fire easily, but very big pieces of wood are quite hard to set on fire, he said.

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    Research proves that nearly half of the cancers diagnosed(诊断) in the UK each year-over 130, 000 in total- are caused by life choices that include smoking, drinking and eating the wrong things.

    Tobacco(烟草) is the biggest factor, causing 23% for cases in men and 15.6% in women, says the Cancer Research UK report. Next comes a lack of fresh fruit and vegetables in men's diets, while for women it is being overweight. Lead author of the report, Professor Max Parkin, said: "Many people believe cancer is related to fate or in the genes(基因), and that it depends on luck whether they get it or not. Looking at all the evidence, it is clear that around 40% of all cancers are caused by things we mostly have the power to change."

    For men, the best advice appears to be: stop smoking, eat more fruit and vegetables and cut down on how much alcohol you drink. For women, again, the best advice is to stop smoking, but also watch your weight.

    In total, 14 lifestyle and environmental factors, such as where you live and the job you do, cause 134, 000 cancers in the UK each year.

    Some risk（风险） factors are well founded, such as smoking's link with lung cancer. But others are less well recognized. For stomach cancer, a fifth of the risk comes from having too much salt in the diet, data suggests. Some cancers, like mouth and throat cancer, are caused almost entirely by lifestyle choices. But others, like gall bladder cancer(胆囊癌), are largely unrelated to lifestyle.

    Public Health Minister, Anne Milton, said: "By making small changes you can cut your risk of serious health problems- giving up smoking, watching you drink, getting more exercise and keeping an eye on your weight."

    Why do plants grow in some places but not in others? Why does some land have so many plants growing on it, while other land has almost no plants growing on it at all?

    To grow, plants need several things. One is warmth. In very cold places almost nothing grows. Plants also need water. In very dry parts of the Earth only a few unusual plants can grow. That's why there are almost no trees or grass in dry deserts.

    Plants must also have a place to put down their roots and grow. They find it difficult to grow on hard land. The town is built(被建立) on hard land. The plants there have only the soil between the cracks of the stones to grow in.

    Another thing plants must have before they can grow is food. What will happen if we try to make things grow on the sandy beach? A few plants, such as grass, will grow in sand, but most plants won't. Even if the weather is warm enough and we water the plants each day, many of them will die because the sand on this beach has almost no food for plants.

    Sending packets, shopping for everyday goods and even building a house, these are new skills that new robots show at the World Robot Exhibition.

    Obesity (肥胖症) is becoming a problem in our busy society, almost one in three American adults is now considered to be obese. Children obesity is also at an all-time high.

    Obesity means being very overweight. If you are obese, you have too much body-fat. If you eat more food than your body can use, this will make you put on weight. Food that your body does not need will be stored (储存) as fat by your body.

    The following are the major factors (因素) that increase the risk of obesity.

    What you eat plays a major role in weight gain. Eating a lot of fattening food such as hamburgers, sweet drinks, ice creams and other sweet food can increase the risk of becoming obese.

    If you do not do enough exercise, you will put on weight as the food you eat is not being used to make energy for physical activities.

    The chances of your being obese are greater if your parents are obese.

    There are many psychological (心理的) factors that cause people to eat too much. People who are worried, unhappy or bored will often eat to make themselves feel better. This is known as comfort eating.

    Age is another factor, as you tend (趋于) to be less active when you get older. When you get older, you need to eat less, and if you do not eat less, you will put on weight.

    Obesity can cause many health problems such as heart problems, high blood pressure and many other serious medical conditions.