If you answer "Yes" to more than two of these questions, you are one of those people with stress. So what can you do about it?
Doing relaxing exercises, talking with friends and listening to light music are all usual ways of relieving（减轻） stress. However, doctors now say that there are easier ways—people should laugh and smile more often. When you laugh and smile, your body relaxes. They also say that people, especially men, should cry more often, be­cause crying is the natural way of relieving stress.

    Thanks to the Earth, we have fresh air to breathe, clean water to drink and warm sunshine to enjoy. But it seems that we haven't realized that the Earth is facing many environmental challenges and it is getting "sick".

    Scientists say that of all the environmental challenges, climate (气候) change is the biggest one. The temperature on the Earth has risen by more than 0. 5C since 1992. Cities like Singapore and Tokyo that are at low altitudes (海拔) may be covered by the ocean (海洋) in the future.

    But this is not the only problem people are facing. Since 1992, the human population has grown by 2 billion, while the population of all other animals has dropped by nearly 30 percent. At the same time, water pollution has become serious. We are also facing problems like light pollution, noise pollution and some other pollution.

    However, we have made some progress in saving the Earth. For example, we stop using harmful materials to make the hole in the ozone layer (臭氧层) smaller to slow the rise of the temperature. We do a lot of work to help the animals in danger, or more than two-thirds of the worlds wild animals may disappear (消失) by the end of 2020.

    "The progress shows that we can make good changes when we act wisely, "scientists say, "we must take action to protect the environment, or it will be worse."

    A long time ago, people thought that the Sun went round the Earth. In some countries people even said that the Sun was a god (神). They thought the god drove across the sky each day on a golden horse. Now we know the Earth goes round the Sun. It takes the Earth a year to go all way round the Sun. Today men even know how far it is for the Earth to go round the Sun. They tell us that the Earth travels over a thousand miles a minute on its journey round the Sun.

    The Sun is really a star. It is much bigger than the Earth and it is very hot. Some people have been to the Moon but we know that no one can ever go to the Sun. It is far too hot for people to live anywhere near it. The Sun is about three hundred thousand times heavier than the Earth and more than a million times larger.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of radiation from the sun and other stars, which is bad for their health. The damage(危害) done by radiation won't be discovered until their children or even grandchildren are born. Some special medicine may work a little, but no really helpful medicine has been.

    Space junk is also thought a great danger to spacemen. It's reported that there are 9, 000man﹣made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space junk. An explosion(爆炸) in 1996made a cloud of 300, 000 fragments, each at least 4mm in size, and even a small piece of these knocked against a spaceship window and did some damage. Scientists are watching and reporting any possible danger all the time. They are working on helpful ways to do with space junk.

    Although space is really dangerous, it interests everyone on the earth. In the near future, it may become usual for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should care for space and do something to help improve the space environment.