The aztecs first worked for local rulers as soldiers for hire

The triple union that the Aztec Empire had been made out of three tribes, and all of these three tribes were under the rule of other stronger tribes. The Aztecs were vassals, so they had to pay tribute, respect the law of their rulers, and participate in their wars, mainly as a strong shock unit.

Wanting to be free and also under the guidance of their warrior God that according to them decided it was a time for war again, one of the three tribes that formed the Aztecs, the Mexica, led the war against their rulers, and two other vassal tribes, they waged a war more than 120 days long, but finally won.

After the win, the three tribes made a triple alliance and formed the Aztec Empire.

answer; (b); i believe its indefinite existence of human population in a healthy and prosperous condition;