The major reason which necessitates the expansion of agriculture is the increase...

The question is asking why agriculture needs to be expanded. It provides four options to choose from: rainfalls, population, manpower, and animal power.

The correct answer is Option B: population.

Agriculture needs to be expanded because the world's population is increasing. As more people are born and live longer, there is a greater demand for food to feed everyone. To meet this demand, agriculture must expand to produce more crops and raise more livestock.

Expanding agriculture involves increasing the amount of land used for farming, adopting modern farming techniques, using fertilizers and pesticides to improve crop yields, and investing in agricultural research and development. By expanding agriculture, we can ensure that there is enough food to feed the growing population and reduce the risk of hunger and food shortages.

It is important to note that while rainfall, manpower, and animal power are all important factors in agriculture, they are not the main reason for the expansion of agriculture. Rainfall is needed for crops to grow, manpower is required to work on farms, and animal power can be used for plowing and transportation. However, the primary reason for expanding agriculture is the increase in population.

To learn more about this, please read the relevant sections of the recommended textbooks.