Natural selection is most responsible for which of the following?

the development of genetic mutations within a population of organisms

the passing of fatal diseases from one organism to another

the preference that some species have for certain environments

the great number of different species of organisms that have existed on earth

the great number of different species of organisms that have existed on Earth

Explanation:

The great number of different species of organisms that have existed on Earth.

Mutations occur in an alleatory way. According to Darwin (father of Theory of Natural Selection), mutations will make individuals be better adapted or less adapted to their environment. When individuals are better adapted, populations tend to be more likely to survive, reproduce and adapt better.

Due to the large amount of mutations which occur on individuals, Natural Selection generates pressure over species, many tend to adapt and so, millions of species exist.

the answer is:

carbon dioxide