Organisms A and C are most closely related. Notice that the amino acid sequences shown for A and C share Val-Ser in common. Organism B shares no amino acids in common with either A or C for this particular sequence.
The food trickles from the crop into the bird's stomach (proventriculus or gizzard) where digestive enzymes are added to the mix and physical grinding of the food occurs. The gizzard is why chickens do not need teeth.
