The Indus, Ganges, and Brahmaputra were important to ancient India because they were (1) high mountain ranges that protected India from invasion (2) great rivers that flowed through India’s fertile northern plain (3) Aryan gods to whom the priests prayed for rain (4) ruling dynasties that united the people of Harappa and Mohenjo-Daro
The Indus, Ganges and Brahmaputra were great rivers that flowed through India’s fertile northern plains. So the correct option of the given question is option “2”. The banks of these rivers were very fertile for irrigation and farmers used to irrigate the banks to generate huge amount of food crops for the people. These rivers flowed from the mountains and they carried with them fertile soil that they deposited in the banks of the plains. The main occupation of people in those days was irrigation.