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    If you want to live longer and lower the risk of heart disease, a move to the mountains may help. Research by scientists in Greece shows that living in the mountains is good for the heart and longevity(长寿). People living at higher altitude(海拔) have lower possibility of dying from heart disease than those closer to sea level, even if they have factors that could increase their risk. "Residence in mountainous areas seems to have a 'protective effect' from heart disease," said Dr Nikos Baibas of the University of Athens. He and his colleagues suspect that the increased exercise from walking up mountainous area gives the heart a good workout and enables it to cope with lower levels of oxygen.

    Researchers studied the health records and death rates of 1,150 Greeks who lived in three villages near Athens over 15 years. One village was 1,000 meters above sea level and the other two were in low-lying areas. Although men and women living in the mountainous village had higher blood pressure rates and other risk factors than people in the other villages, they had a lower rate of death from heart disease and other causes after a fifteen year follow-up." The contrast was more evident among men than among women," Baibas added in a report in the Journal of Epidemiology and Community Health. Heart disease is one of the world's top killers. Smoking, high blood pressure, raised cholesterol levels, being overweight and a family history of the illness increase the possibility of developing the disease.

已知一颗粒子等可能地落入如右图所示的四边形ABCD内的任意位置，如果通过大量的实验发现粒子落入△BCD内的频率稳定在$\frac{2}{5}$附近，那么点A和点C到时直线BD的距离之比约为（    ）

    You may be surprised to learn how many animals actually have a memory. 1 your goldfish can show evidence (证据) of learning ability. If you have a pet fish, try this 2. Every day when you feed the fish, sprinkle (撒) the food only in the same location.

    Keep a record of daily observations (观察) of the fish, taking down notes about the fish's swimming directions or behavior whenever you come to feed it. Before long, the fish should swim to the spot where you sprinkle the food whenever you approach (靠近) the tank. See how it reacts (反应) to your approaching the tank and take notes before, 3, and after your experiment.

In this example of animals' memory, we don't really know if your fish knows the fact that you are going to feed it. But it has showed its 4 ability to learn and to remember.

    Bees 5 with each other in a way which shows an intelligent memory. When a bee finds a good location for gathering nectar (花蜜), it will remember 6 to get to this location from its hive (蜂巢). The bee then returns to the hive and passes along its memory by doing a complex dance to inform the others of where the food was found. It uses wings, legs, antennae (触角) and body to deliver the message. When the dance is over, other bees fly to this location to bring back food for the hive.