Billy thinks evolution is slow and continuous. He believes in

The correct answer is - Gradualism.

Explanation:

Gradualism is the theory that new species evolved from existing species through progressive, frequently subtle changes as opposed to through unexpected, significant changes. The little changes are accepted to bring about distinguishable changes over long periods of time.

Gradualism is a model that explains the process of evolution that alludes to the minuscule varieties in a life form or in the society that occur after some time to improve a fit for creatures and people in their condition. These varieties permit them to endure and flourish, bringing about the moderate and predictable procedure of progress in the entire populace.

Thus, the correct answer is - Gradualism.