题目

In China, many people are leaving the countryside to find jobs in the cities, because the countryside is much poorer than the city, and often there isn't much work there. Services such as hospital and transport are usually much better in the city than in the countryside. They hope that their lives will improve when they move to the city.    But in the big cities of Europe like London or Paris, people are moving out of the city. These rich families want to live a quieter life. They are tired of the noise and the dirt of the city, and they are tired of the crowded streets, crowded trains《晏子使楚》是我们比较熟悉的古代故事，在这个故事中有这样一句话﹣﹣“橘生淮南则为橘，生于淮北则为枳”，你认为产生这种现象的最主要的因素是（ ）A．地形 B．土壤 C．水源 D．气候