They live in the same habitat and niche. They forage and eat the same type of food. They mate and produce fertile offspring. They are similar in appearance and color.
I gave my students this multiple choice question: Which factor determines if two individuals are members of the same species?

Only one answer is correct among these 4 choices:
- They live in the same habitat and niche.
- They forage and eat the same type of food.
- They mate and produce fertile offspring.
- They are similar in appearance and color.

Could you tell me which one is correct?

They mate and produce fertile offspring.