The two factors that are most important in determining the density of air are:
a. temperature and ozone.
b. temperature and salinity.
c. temperature and water vapor content.
d. nitrogen and water vapor content.
e. carbon dioxide and water vapor content.

c. temperature and water vapor content.

Explanation:

The density of any substance is dependent of temperature, and in gases, the variations is greater than in any other substance, therefore, temperature is very important to calculate air density. Also, the concentration of water vapor in the air can vary depending  where is located, and that concentration will affect the density because it affects the average mass of air.

c. temperature and water vapor content is the correct answer.

Explanation:

temperature and water vapor content are the two most important in determining the density of air.

When the temperature gets increase it results in the increase of volume and density gets decreases.

Temperature is an important factor to determine the air density.

The concentration of water vapor in the air change depending on where it is placed and so when water vapor is added it will change the density of air because it changes the average mass of air and density gets decrease.