can produce fertile offspring. can communicate easily. will defend their territory. will move from place to place.
I gave my students this multiple choice question: Species are classified based on their characteristics. Which characteristic identifies two organisms as members of one species? The organisms

Only one answer is correct among these 4 choices:
- can produce fertile offspring.
- can communicate easily.
- will defend their territory.
- will move from place to place.

Could you tell me which one is correct?

can produce fertile offspring.