Answer:
the answer is A.
Explanation: According to the map the major growth of population in china has occurred in south of China of it's rich farmland. It is shown in the map that in some parts of southern China population has increased almost 1000% which indicates the population blast. Also in other parts of south it is shown that population increased at a higher percentage. China is a major producer of peanuts,some oilseed crops like as sesame seeeds,rapseed seeds, sunflower seeds which are vastly grown in southern China. Citrus is also a major cash crop in southern China.
So for rich farmland in southern China has worked as a key factor increasing the population.