In the photograph below, two fish are displaying a behavior commonly observed among pairs of rabbitfish. While one has its head down feeding on coral, the other remains upright, alert for predators. This behavior continues to be present in the rabbitfish population because A) this behavior was learned by observing other fish species B) both fish could not fit into the small spaces in the coral C) this behavior increases their chance of survival D) the fish species needed to become alert to survive