MSG(monosodium glutamate谷氨酸单钠) is a food additive(食品添加剂),which has been widely used by many food factories all over the world since it appeared first in Japan in 1909.

    MSG is a substance that is added to some food to improve its taste and color. It is used in foods around the world such as cakes, bread, frozen meat, fish and vegetables. In the beginning, people thought MSG was safe just like salt and sugar. However, in 1968 some people reported they seemed to have bad reactions(反应) to MSG after having had a meal at a restaurant. They included headaches and quick heartbeat . It was also reported that MSG excited a person's brain and caused his death in Japan. Scientists think that MSG may lead to many neurological disorders(神经紊乱). In mice studies done by a university, the result showed the mice didn't want to eat the food including MSG.

    Today many food companies “hide” MSG on food labels(标签) by using different names. If you see “natural flavorings (调味品) ”,“hydrolyzed protein” and  “spices” in a food label, you are probably seeing a hidden way to “report” MSG in a food label. Every time we have a meal in a restaurant, we always feel the food very delicious to taste, but sometimes it is dangerous for our health because some harmful food additives have been added to the food.

    To protect people's health, our governments, from central to local, are taking action to stop factories producing harmful food additives.

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    Rivers are one of our most important natural resources(资源). Many of the world's great cities are located on rivers, and almost every country has at least one river through it that plays an important part in the lives of its people.

    Since the beginning of history, people have used rivers for transportation. The longest one in the United States is the Mississippi. The lifeline of Egypt is the Nile. To the people of India, the Ganges is great, but it is also important for transportation. Ships can travel along it for a thousand miles. Other great rivers are the Congo in Africa and the Mekong in southeastern Asia. The greatest of all for navigation(航海), however, is the Amazon in Brazil. It is so wide and so deep that large ships can go about two thousand miles up it.

    Besides transportation, rivers give food, water to drink, water for crops, and chances for fun and recreation for the people who live along their banks. In order to increase the supply of water for crops, engineers sometimes build a dam(坝) across a river and let a lake form behind the dam. Then people can use the water not only to irrigate(灌溉) their fields but also to make electricity for their homes and industries.

    However, large cities and industries that are located on rivers often cause problems. As the cities grow in size and industries increase, the water in the rivers becomes polluted with chemicals and other materials. People are learning the importance, however, of doing more to keep their rivers clean if they want to enjoy the benefits of them.

    A fish that lives in America can live out of water for months at a time, similar to how animals got used to land millions of years ago, a new study shows.

    The Mangrove Rivulets, a kind of little fish, lives in small pools of water. When their living place dries up, they live on the land, said Scott Taylor, a researcher in Florida.

    The fish can grow as large as three inches. They group together and breathe air through their skin before they can find water again.

    The new scientific discovery came during a trip.

    "We were travelling for fun. And one day I kicked over a log (圆木) and the fish came out." Taylor told reporters by telephone. He said he would make his study on the fish known to the public in an American magazine early next year.

    In lab tests, Taylor said he found the fish can live up to 66 days out of water without eating.

    Some other fish can live out of water for a short period of time. The walking catfish found in Southeast Asia can stay on land for hours at a time, while lungfish(肺鱼) found in Australia, Africa and South America can live out of water, but only in a not active(活跃的) way. But no other known fish can be out of water as long as the Mangrove Rivulets and keep active, according to Patricia Wright, a biologist at a Canadian University.

    More studies of the fish may tell how animals changed over time.

    "These animals live in conditions similar to those millions of years ago, when animals began to move from water onto land." Wright said.

    There are lots of objects that we see in the sky. During the day we see the sun. After the sunset in the evening, we see mostly the stars. Not all the lights in the sky that we see are really stars.

    Of course, we see the moon. Some of the other lights in the sky are planets. Planets revolve (转动) around the sun like earth does.

    Once in a while someone will see what they call a shooting star.

    Shooting star looks like a star that is moving quickly across the sky. Some people believe that seeing a shooting star will bring them good luck. It's hard to find shooting star because they disappear fast.

    The correct name for a shooting star is meteor. Besides very large objects like stars, planets and moons, space has lots of little objects. These can be rocks in space left over from old planets.

    These objects can even be as small as dust. These objects are called meteorites(陨石).

    When a meteorite gets close to the earth, it gets pulled towards the earth by gravity. Earth is surrounded by atmosphere. Atmosphere is made up of air and clouds. A meteorite blows up in the earth's atmosphere. This makes the short bright moving light in the night sky. A meteorite thus turns into a meteor.