题目

The world is divided into two main parts. The difference is ___41___one part is rich and the other is poor. In the poor part,  a lot of people ___42_____get enough to eat. In the rich part, a lot of people eat too much. In one part ,children starve and in the other, a lot of people get fatter and have to go on diets, or do some exercise in ___43____ to lose weight.The poor countries are called the ____44______ countries. They have special problems. Sometimes the land is too poor to grow anything ____45___. The land can be ___46___, but a lot of things must be done first. New ____47____ method若双曲线上一点P到右焦点的距离为8，则P到左准线的距离为    ．