C)India's population was able to grow throughout the postclassical era because the advancements in farming made cultivation easier. Thus, there was more food and a better economy to sustain a larger population.

A) Monsoon season provided the necessary rain that the crop needed to thrive in the Indian River Basin during the hot summer months of June through September. This allows farmers to continue to cultivate their land and create irrigation systems.

Agriculture

B) The irrigation system consisted of several dams of various sizes barrages and tube wells.