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2017年高考英语二轮专题复习命题预测58 阅读理解 阅读下列短文，从每题所给的四个选项中，选出最佳选项。 A Some trees can survive a long time without water. Think of trees that grow in the desert. But other trees may need more moisture (水分)than they can get from rainfall or from the air . Trees and other plants can look thirsty. Leaves can become weak and hang downward. They can also turn yellow. Yellowing can be a sign of too much water. But it can also be a warning sign of too little water. With a newly planted tree, the roots have not yet spread out from the root ball. The root ball can become dry faster than the dirt around it. So put water on the area of the root ball and the surrounding soil until the roots become established. Once a tree is well established, water deeply instead of watering often. The amount of water needed depends on the tree and the soil. Clay(黏土) soils hold water for longer periods while sandy soil holds less water. During the hottest season, a deep watering may satisfy a tree for anywhere from ten days to four weeks. Ted Swiecki is a plant scientist . He says people should not water established trees at the base of the trunk（树干）. This can harm the tree. Too much water in the soil at the base of a tree can lead to the growth of fungi（菌类）. If the area is too wet, harmful organisms have a better chance to invade the tree and cause disease. | 
