Assertion (A) : Pro-social behavior is based on an inborn, natural tendency in human beings to help other members of their own species.
Reason (R) : The inborn tendency facilitates survival of the species.

Both A and R are true, and R is the correct explanation of A

The correct answer is option 1: Both A and R are true, and R is the correct explanation of A

Assertion (A) : Pro-social behavior is based on an inborn, natural tendency in human beings to help other members of their own species. True. Pro-social behavior (like helping, sharing, and cooperating) is believed to be an inborn, natural tendency in humans to support others, especially members of their own species.
Reason (R) : The inborn tendency facilitates survival of the species. This is also true. This natural tendency to help others increases the chances of survival of the species — which is an important concept in evolutionary psychology.

And here, R correctly explains A because it gives the biological reason why humans have an inborn tendency toward pro-social behavior.