It guarantees the survival of a species. It increases the size of a population. It requires the individuals to be identical. It happens over a long period of time.
I gave my students this multiple choice question: Which statement best describes the theory of natural selection?

Only one answer is correct among these 4 choices:
- It guarantees the survival of a species.
- It increases the size of a population.
- It requires the individuals to be identical.
- It happens over a long period of time.

Could you tell me which one is correct?

It happens over a long period of time.