Final answer:
Horse (C) has anuclear red blood cells (RBCs) because it is a mammal, and mammalian erythrocytes typically do not have nuclei.
Step-by-step explanation:
The species with anuclear red blood cells (RBCs) among the options provided is the horse (C). This is because mammalian erythrocytes, which include horses, do not have nuclei, whereas birds have nucleated erythrocytes. Other vertebrates such as fish and amphibians also have nucleated red blood cells. Mammalian red blood cells are characterized by the absence of nuclei at maturity, which is a significant distinction from the erythrocytes of birds and other vertebrates. The principal function of erythrocytes is to carry and deliver oxygen to the tissues across various species.