【阅读选择】Climate scientists are not present everywhere. Because there are so many places in the world and not enough scientists to observe all of them, they're asking for your help in observing signs of climate change across the world. The citizen scientist movement encourages ordinary people to observe a very specific research interest—birds, trees, flowers budding, etc, and send their observations to a giant database to be observed by professional scientists. This helps a small number of scientists track a large amount of data that they would never be able to gather on their own. Much like citizen journalists helping large publications cover a hyper-local beat, citizen scientists are ready for the conditions where they live. All that's needed to become one is a few minutes each day or each week to gather data and send it in. In “All that's needed to become one... (paragraph 2) ”, what does the word “one” stands for ?

【阅读选择】Do you think sitting and studying all the time will improve your grades? Think again. Getting some exercise may help, too. New research with older people suggests that taking regular walks helps them pay attention better than if they didn't exercise. Walking regularly helps elderly people ______.

【阅读选择】Organisms have a great variety of ways of adapting. They may adapt in their structure, function and genetics, in their development and production of the young and in other respects. An organism may create its own environment, as do warm-blooded mammals, which have the ability to adjust body heat exactly to maintain their ideal temperature despite changing weather. Usually adaptations are an advantage, but sometimes an organism is so well adapted to a particular environment that, if conditions change, it finds it difficult or impossible to readapt to the new conditions. The author cites the behavior of warm-blooded mammals in order to show that a living thing may have the ability ______.

【阅读选择】Many researchers，whose work depends on ocean sounds object to a limit of one-hundred-twenty decibels(分贝). They say such a limit is a greater danger than they believed. They want to prevent noises from harming creatures in the ocean. According to the passage, what will scientists most probably do in the future?

【阅读选择】Two thousand years ago the Chinese had already developed a working compass. A piece of lodestone(天然磁石) would be cut into the shape of a ladle(长柄勺). Placed on a stone board with a smooth surface, the lodestone would move round until the "handle" of the ladle pointed south while the bulk(主体) of the ladle was attracted to magnetic north. This interestingly shaped device is mentioned in a book from about 80. Other ancient books may have dated it as far back as the fourth century Jade(玉石) finders played an important role in the invention of the "ladle". They travelled great distances to look for jade. In order not to lose directions, they would take a "ladle" with them. When did the Chinese invent the compass?

【阅读选择】The world is not only hungry; it is also thirsty for water. This may seem strange to you, since nearly 75% of the earth’s surface is covered with water. But about 97% of this huge amount is sea-water, or salt water. Man can only drink and use the other 3%—the fresh water that comes from rivers, lakes, underground, and other sources. And we cannot even use all of that, because some of it is in the form of icebergs(冰山) and glaciers(冰川). Even worse, some of it has been polluted. What percentage of the earth’s water can man actually use at present?

【阅读选择】We are so used to our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted. Because we can feel that things are heavy, we think of "weight" as being a fixed quality in an object, but it is not really fixed at all. If you could take a one-pound packet of butter 4, 000 miles out from the earth, it would weigh only a quarter of a pound. How much would four pounds of tea weigh if it was taken 4,000 miles out from the surface of the earth?

【阅读选择】Good news for chocoholics：the treat preferred by millions all over the world is good for you, according to American researchers at the University of California．Chocolate contains substances called flavonoids(类黄酮) that can help maintain a healthy heart and good circulation．The researchers have discovered that cocoa acts like aspirin and that eating a bar of chocolate has also been shown to release endorphins in the body：these chemicals help to reduce pain and stress and make you feel happy.Why is chocolate good for heart and circulation?

【阅读选择】The ideal battery will store a lot of energy in a small package. Right now, Belcher's model battery, a metallic disk completely built by viruses, looks like a regular watch battery. But inside, its components are very small—so tiny you can only see them with a powerful microscope.Which of the following is true of Belcher's battery mentioned in paragraph 6?

【阅读选择】But just like your alarm clock, your internal clock can be reset. In fact, it automatically resets itself every day. How? By using the light it gets through your eyes. Scientists have known for a long time that the light of day and the dark of night play important roles in setting our internal clocks. For years, researchers thought that the signals that synchronize the body's clock were handled through the same pathways that we use to see.Which of the following statements is NOT true according to the fourth and fifth paragraphs?