Which subsystem includes the air we breathe

It is Oxygen because we breath it out

All of the following were reasons why the Aztecs were defeated by Cortes except Aztec alliances with other tribes.

Option D

Explanation:

Defeat of Aztecs is marked as the beginning of Spanish colonial rule over America. Spanish forces were headed by Hernan Cortes who received the support of other allies which majorly the enemy tribes of Aztecs.  

Some of reasons of defeat of Aztecs apart from Spanish alliance were widespread epidemic of smallpox which killed large chunk of its population and also the use of inferior weapons (gun powders) in the battle against the advanced and superior artillery of the Spanish army.