Which Experiment Most Closely Confirms the Linkage Between DNA →

Which experiment most closely confirms the linkage between DNA → a gene → a gene product → the behavior that results from that product?

A) experiments with the inland and coastal garter snakes and their food preferences
B) experiments with identical twins separated at birth
C) experiments with laughing gull chicks and their pecking behavior to solicit food from the mother gull
D) experiments with white-crowned sparrows and the critical period for learning bird songs
E) experiments with Aplysia snails and their egg-laying behavior