What are the chances of getting pregnant without protection?

The risk of having unprotected sex and getting pregnant three days prior to ovulation is 15%. You will have a 12% chance on the ovulation day. In the real world, large studies show that women who engage in unprotected sex during mid-cycle have a much lower chance of getting pregnant as the risk is around 5.8%.

C) they are specialized meaning they are designed to do different things

Probably a behavioral adaptation