Yang Nan, 17, was happy to move to her new home in a northern area of Beijing. She was told that her neighborhood used to be rich farmland planted with vegetables, corn and wheat. But looking at the new road, beautiful parks and supermarkets, to her surprise, Yang couldn't see any sign that food was once grown there.
    Yang is not alone. In recent years, many Chinese people have moved into new houses in country areas. Tall buildings have been built everywhere in the suburbs. The crops and fruit trees are no more grown there. But these changes have caused big problems too, warns Gan Zangchun, an official（官员）at the Ministry of Land and Resources(国土资源部）．
    "Chinese cities are growing very fast. This has made the area for farmland much smaller than before. This is really bad for the country's ability to grow food, not to mention the lives of farmers," said Gan last Monday.
    As the population of China is growing all the time, the country needs more farmland to grow food for the increasing people of China. But the recent rise in house prices has made selling land a good business. A lot of land has been used to build new houses for sale. So you can see, the shortage of the farmland is now a very serious problem.
    Pollution, such as, oil pollution, industrial(工业) pollution and water pollution, which makes land useless, is another reason for the big drop in China's farmland. About 2.67 million square kilometers of land in China have been polluted and turned into desert.
    Today, can we use less farmland to grow enough food for more people? Of course not! The government wants China to have at least 120 million hectares（公顷） of farmland. Only in this way can we raise such a big population. But there are only about 121.8 million hectares left. "It will be really difficult to reach the goal", Gan said. He said that the government would fight illegal(非法的) land use and something useful must be done to stop farmland from becoming desert.

下列关于如图说法正确的是（　　）

甲、乙、丙、丁四位同学各自对A，B两变量的线性相关性做试验，并由回归分析法分别求得相关指数R与残差平方和m如下表：

则哪位同学的试验结果体现A，B两变量更强的线性相关性（　　）