The is the ultimate cause for balancing a population.

age structure

breeding pattern

environment

all of the above

Option D, all of the above

Explanation:

All the demographic components are very essential for balancing the population of any species be it human or animals. The major components of demography are age, sex, average age of mating, average number of children per family, etc.  

All these components of demography/population are affected by environmental conditions. In favorable environmental condition, species/organism mates with each other to produce healthy offspring which could result into a well distributed age structure of the population thereby balancing the population.

Option D, All of the above

oak trees? ? what was listed

a. the production of carbon dioxide through the process of photosynthesis