Concept:The number of heart chambers in vertebrates differs across classes and helps identify the animal type.Explanation:A fish heart has one auricle and one ventricle.An amphibian heart has two auricles and one ventricle.Most reptiles show a partly divided ventricle, while birds have two auricles and two ventricles.Since the dissected specimen has two auricles and one ventricle, it matches the amphibian heart plan.Therefore, the animal is most likely an amphibian.Answer:C. amphibian