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第4部分：阅读理解 下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。 Salty Rice Plant Boosts Harvests British scientists are breeding a new generation of rice plants that will be able to grow in soil containing salt water. Their work may enable abandoned farms to become productive once more. Tim Flowers and Tony Yeo, from Sussex Universitys School of Biological Sciences, have spent several years researching how crops, such as rice, could be made to grow in water that has become salty. The pair have recently begun a three-year program, funded by the Biotechnology and Biological Sciences Research Council, to establish which genes enable some plants to survive salty conditions. The aim is to breed this capability into crops, starting with rice. It is estimated that each year more than 10m hectares (公顷) of agricultural land are lost because salt gets into the soil and stunts (妨碍生长) plants. The problem is caused by several factors. In the tropics, mangroves (红树林) that create swamps (沼泽) and traditionally formed barriers to sea water have been cut down. In the Mediterranean, a series of droughts have caused the water table to drop, allowing sea water to seep (渗透) in. In Latin America, irrigation often causes problems when water is evaporated (蒸发) by the heat, leaving salt deposits behind. | 
