The correct answer is A: the Spanish have won over the Aztecs (partially with the help of people that the Aztec had conquered before, such as the Tlaxcaltecas) and the Aztec civilisation was destroyed. There are still some people speaking Nahuatl today though
in order to avoid any form of betrayal or deceipt, they need to set on rules to avoid loopholes or betrayal, it could also provide proof of the agreement and ensure that everything was done efficiently and without mistakes