Cortez was viewed as a god to the Aztecs. When he arrived, the proficized that a white bearded god would come and visit them, and it just so happened that that happened during the same year. So what happened is that upon arriving and speaking with Aztecs they realized that they could not defeat them upfront with their own forces so they decided to ally with the enimies of the Aztecs. They couldn't have slashed and burned nor could they have destroyed everything in their path because they were too small of a force. And treaties were clearly not just as look at what happened to the Aztecs.
CORRECT ANSWER D formed alliances with the enimies of the aztecs