Select three findings that show that behavior has a genetic component. A. It was found that mice who do not engage in nurturing, maternal behavior with their newborns lacked a certain gene that produces a specific protein. B. Scientists isolated an egg-laying hormone (a protein) that causes the marine snail Aplysia to lay eggs even if it has not mated. C. When two species of lovebirds were interbred, the hybrid birds had difficulty carrying nesting material. D. Chicks of laughing gulls improve their ability to peck a parent's bill in order to get the parent to regurgitate food during the first few days in the nest.