Which is an example of adaptive social behavior?

A male deer tries mating with a female and is chased off by another male, but the original male finds another mate.
The grass that a rabbit usually eats is hard to find one season, but the rabbit finds another temporary food source.
Frogs and their young have coloration that enables them blend in to their environment so they can sneak up on prey.
Birds help take care of each other's young to increase their chances of survival, and the behavior is passed on to offspring.