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website to sell a computer you used at college. Your advertisement may include its brand, specifications/features, condition and price, and your contact information.You should write at least 120 words but no more than 180 words. Write your essay on Answer Sheet 1.
2017年6月英语四级作文真题：卖电脑

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从散点图上可以看出员工人数与产量有任何关系吗？

什么是回归系数？它的统计含义是什么？

度量用估计回归方程能够解释的变化比重的指标称_______。

. During vigorous exercise, our muscles tire as they run out of fuel and build up waste products. Muscle performance can also be affected by a phenomenon called "central fatigue," in which an imbalance in the body's chemical messengers prevents the central nervous system from directing muscle movements effectively. It was not known, however, whether central fatigue might also affect motor systems not directly involved in the exercise itself—such as those that move the eyes. To find out, researchers gave 11 volunteers a carbohydrate solution either with a moderate dose of caffeine—which is known to stimulate the central nervous system—or as a placebo without, during 3 hours of cycling. After exercising, the scientists tested the cyclists with eye-tracking cameras to see how well their brains could still control their visual system. The team found that exercise reduced the speed of rapid eye movements by about 8%, preventing their ability to capture new visual information. The caffeine—the equivalent of two strong cups of coffee—was sufficient to counteract this effect, with some cyclists even displaying increased eye movement speeds, the team reports today in Scientific Reports. So it might be a good idea to get someone else to drive you home after that marathon.