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课时作业12 Healthy eating Ⅰ.阅读理解 (2017·湖北省重点中学联考) “Eat local.” It's one way to reduce human effect on the planet. Eating local means to try to buy and consume foods that are grown in places close to home. However, most of the food sold at supermarkets is not locally grown or produced. Trucks and planes deliver these foods from hundreds or thousands of miles away. During the transportation, greenhouse gases are produced, causing global warming. So the shorter the distance your foods must travel, the less the harm is done to the environment. But how do you get local food if you live in a large city, hundreds of miles away from farms ? Environmental health scientist Dickson Despommier and his students came up with the idea of a “vertical(垂直的) farm”． A vertical farm is a glasswalled structure that could be built as tall as a skyscraper. Since the garden is built upwards, rather than outwards, it requires much less space than an ordinary farm. The world is quickly running out of room for ordinary farming. Vertical farms could be a key to this situation. Despommier imagines a 30story building with a greenhouse on every floor. The walls of the building would be clear, to allow crops to get as much sunlight as possible. Depending on a city's water resources, Despommier thinks hydroponic(水培) farming is another method for the vertical farm which needs no soil to grow plants. | 
