图甲示意我国某区域的水系分布。某学校研究性学习小组对图甲中的M地进行实地考察，并查阅了相关资料，发现近30年来M地生态环境明显改善。图乙示意M地的等高线分布，表格示意M地的土地利用结构变化。读图、表，回答下列问题。

甲                          乙M地的等高线地形图（单位：m）

（2）根据图表材料，分析M地生态环境明显改善的原因和对R河水文特征的影响。（8分）

（3）N湖泊周围的平原地区是我国重要的商品粮生产基地，试评价其成为商品粮生产基地的有利条件。（8分）

  Because neither she 48  her husband smoked, Mrs. Trench was surprised to see cigarette ash on her doorstep as she entered the house. When she opened the living room door, she was astonished to see a strange man fast  49  in an armchair! Taking care not to disturb him, Mrs. Trench left the house at once. She called a taxi and went  50  to the police station. When she got there, she lost no time to explain  51  had happened and added that the man must have got into the house through  52  open window. Mrs. Trench returned home  53  a police car together with two policemen. 54 it was too late: the man had disappeared. Hurrying upstairs, she went to her dressing table. She smiled with relief when she saw the only thing that the man had taken was an imitation diamond necklace that was almost  55  !