Most of the flowers in nature are red, orange and yellow. If we have seen a black flower, it's chance in a million.

    People have made a survey to colors of more than four thousand kinds of flowers and discovered that only eight of them are black.

    As we know, sunlight is formed by seven colored lights. The wavelength of each light is also different, so the quantity(量) of heat in each light is also different. Flowers, especially their petals(花瓣), are easy to be harmed by high temperature.

    Black flowers can take in the light of all the wavelengths that make them dry up because of high temperature, so black flowers can hardly resist(抵抗) sunlight. But red, orange and yellow flowers can protect themselves from sunlight by reflecting(反射) the red light, orange light and yellow light, each of which has a large quantity of heat.

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    Different weather makes people feel different.It has an effect on health，intelligence(智力) and feelings.

    In August，it is very hot and wet in the southern part of the United States.People there have heart trouble and other kinds of health problems during this month.In the Northeast and the Middle West，it is very hot at some times and very cold at other times.People in these states have more heart trouble after the weather changes in February or March.

    The weather can also influence intelligence.For example，in a 1983 report by scientists, the IQ(智商) of a group of students was very high when a very strong wind came，but after the strong wind，their IQ was 10% lower.The wind can help people have higher intelligence.Very hot weather，on the other hand，can make it lower.Students in many schools of the United States often get worse in exams in the hot months of the year(July and August)．

    Weather also has a strong influence (影响)on people's feelings.Winter may be a bad time for thin people.They usually feel cold during these months.They might feel unhappy during cold weather.But fat people may have a hard time in hot summer.At about 18℃，people feel more comfortable.

    Are you feeling sad，tired，or unhappy today？It may be the weather's problem.

    When we talk about the universe, we mean not only the earth, the sun and the moon, but also the stars and space between them. There are millions of stars in our sky. The sun is one of them. Around it there are eight big planets moving, including the earth. The moon is our nearest neighbor in space. If you look at the sky on a clear night, it is possible to see about 3, 000 stars. They look small, but they are really very big hot balls of burning（燃烧着的）gas. Some of them arc huge（巨大的）, but others are much smaller like our planet Earth. The biggest stars are very bright, but they can only live for a short time. Every day new stars are born and old stars die.

    All the stars are very far away. The light from the nearest star（except the sun）takes more than four years to reach the earth.

    Hundreds of years ago, people used stars, like the North Star, to know which direction（方向）to travel in.

Today you can still see that star.

    For thousands of years, humans have explored(探索)the Earth. Nowadays, we are exploring space. Astronomers (天文学家) are the modern﹣day explorers, Now, many astronomers are looking for new planets and new places for humans to live in the future. But where do astronomers start looking？

    First of all, astronomers look for a star. That's because our own Earth moves around a star (the Sun). More importantly, it is the correct distance( 距离) from the Sun for heat and light. So when astronomers have found the star, they look at the planets around it. In recent years, astronomers have found nearly 400 new planets with stars. However, many of these planets are either too near to the star or too far away.

    However, if the planet is in a good position, astronomers look for three key things: water, air and rock. Water is important because all life needs water. Humans can drink it and they can also grow plants with water. And plants produce air for humans to breathe and food to eat. Rock on a planet is also important. That's because there is often water under the rock.

    After many years of scrutinizing, astronomers have found a planet that is similar to the Earth. It's Gliese 581g and it's near a star. The astronomers think it has water and rock and the average(平均的) temperature is between -31℃ and -12℃.That's cold, but not colder than Antarctica or the Arctic Circle, for example. Gliese 581g is bigger than the Earth. A year on Gliese 581g is only 37 Earth days instead of 365. But astronomers do not think these are big differences and some of them think Gliese 581g will be a new Earth. However, Gliese 58Ig is twenty light years from the Earth.

    Which animal do you think is "the king of the animals", the elephant, the lion or the tiger? They are all large and strong. But I think the tiger is "the king of the animals". If you watch carefully, you can find some black lines on the tiger's forehead(前额). The lines look like the Chinese word "WANG". The word means "the king of the world" in Chinese.

    Most of the tigers come from China and India. Tigers are dangerous animals. They look scary(吓人的). They like eating meat. They have yellow fur with black lines. They usually weigh about 200 to 300kg. Tigers can run fast. They run at a speed of 20 meters per second.

    Some people think they are dangerous. But they don't know tigers are in danger now. There are only 20 to 30 wild South China Tigers in China and less than 300 in the world. Lots of people kill them for their fur. We should take action to protect them.