A. The summer monsoons provided the necessary rains and moist air for the crops so that the farmers could supplement with irrigation in the dry fall and winter months. 

B. Due to southern India's arid landscape, irrigation was almost necessary. A bounty of dams, reservoirs, canals, wells, and tunnels were built all over the land. Some reservoirs were lined with brick or stone and captured the rains of spring and summer and allowed a canal to carry the water away to fields during the dry seasons. 

C. Increased productivity in the government, economy, trade, and agriculture allowed for the expansion of population in the postclassical era.

Agriculture