Noise pollution is doing much harm to our health now. Noise，in fact，is unwanted sound and is a kind of invisible (无形的) killer. More and more students enjoy listening to music very much. When they listen to MP3 players, they like to turn up the volume (音量). Some people love listening to loud music. Furthermore, while watching TV, they keep the volume up. But they haven't realized that the noise is weakening their hearing. In fact, the noise not only influences each member in the family, but also makes a difference to the comfort of neighbors.

    Noise pollution is a source of increasing misery (痛苦) to people in our society. If people are often disturbed by it, they may feel uncomfortable or upset. What's worse, the noise can make people mad sometimes. If a worker works in a printing factory for too long, his/her hearing loss is much faster than a common person working in a quieter environment. So everybody must pay more attention to noise pollution. Generally speaking，the following four types of noise should be watched out for：

    Noise in the street

    Construction site (建筑工地) noise

    Noise at work

    Transportation noise

    I think the local department (部门) should take measures to control the noise levels, but it's everybody's duty to keep a quiet environment.

    In 1969, humans landed on the moon for the first time. Now, many other countries want to go there as well. Why?

    The moon has a lot of minerals (矿物质) and other useful things. We want to find out if we can use them. The moon is our closest neighbor in space. We can use it as a rest station. Then, we can learn more about other planets far away in space.

    The moon is 3,474 kilometers in diameter (直径). It is about one-fourth the size of Earth. If Earth is the size of a basketball, the moon is the size of a tennis ball.

    The moon has much less gravity than Earth. If you can jump 1.5 meters on Earth, you can jump 9 meters on the moon.

    The moon is very quiet. There is no sound there. There are a lot of grey rocks on it. The moon's sky is always black.

    Our moon is about 384,400 kilometers away from Earth. The total length of the Great Wall is about 21,200 kilometers. We would have to put about ____ Great Walls end to end to reach the moon!

    Can trees talk? Yes, but not in words. Scientists have reasons to believe that trees do communicate with each other. Not long ago, researchers learned some surprising things. Some caterpillars(毛毛虫) attacked a willow tree(柳树) in the woods. The tree changed the chemistry of its leaves and the leaves tasted so terrible that the caterpillars stopped eating them. Then even more surprising, the tree sent out a special vapour (蒸气) a signal causing its neighbours to change the chemistry of their own leaves and make them less tasty.

    Communication, of course, doesn't need to be always in words. We can talk to each other by smiling, raising our shoulders and moving our hands. We know that birds and other animals use a whole vocabulary of songs, sounds and movements. Bees dance their signals, flying in certain patterns that tell other bees where to find nectar(花蜜) for honey. So why shouldn't trees have ways of sending messages?

    Can we "design" a baby like we design a handbag? It may sound crazy, but a "designer baby" could be possible now. Of course, at the same time, there are both agreements and disagreements with it.

    The "designer baby" idea comes from the research that allows scientists to make changes to human DNA and genes (基因). Usually, it is done when the baby is still just an embryo (胚胎). By doing that, scientists hope that "designer babies" will less possibly be born with some certain serious illnesses.

    During the 21st century, the idea became so popular that the research developed very quickly. Now, it has been firstly used to help born babies with their illnesses. One example of this is that Dr. Adrian Thrasher of University College London was able to save a 1-year-old child from leukemia (白血病) with the help of it. People learned that it was not only illnesses they could change, but also a baby's gender and looks. A well-known event happened in 1996. An American couple, Monique and Scott Collins, decided to use this research to help them choose the gender of their next baby. They wanted to have a baby girl for they have had three sons. Moreover, people could also decide babies' eye color, hair color and even things like height or how sportive babies will be.

    Some people argue that it is not ethical (道德的)to design babies like designing a bag. It is strongly against the nature's rules. Besides, it may not have any bad influence on the baby now, yet no one knows what will happen to him and his children after many years.