You are presented with the question "the average number of individuals per unit of area or what can vary considerably?" and the following answer choices: 
- Decibels
 - colors
 - dense
 - Summer
 - volume
 - seasons
 - animals
 - decreases

Now knowing that population density is the average number of individuals per unit of area or volume and population density varies considerably, choose the best answer.


 

     volume    