Aztec were able to become part of the noble class through acts of bravery during times of war.
a. knights
c. commoners
b. unskilled workers
d. slaves

The correct answer is C. Aztec commoners were able to become part of the noble class through acts of bravery during times of war.

Explanation:

Although commoners were poor and inferior to those who belonged to what we might call the Aztec aristocracy, there was one thing they had, and that was their freedom. They had their families and each other. It was not unheard of, however, for someone from the lower class to become a noble through the courage to face military service or even marriage.

dirty, contaminated water

contaminated food,

chlostrophobic living spaces,

mice infestation,

etc,

the steam engine.

the locomotive.

the telephone.

the telegraph.

the internal combustion engine.

the rifle.

ironclad ships.

electricity/light bulb.