Circulatory Pathways

• Mammals, birds, and crocodiles all have four-chambered hearts. A four-chambered heart is an efficient way to separate oxygen-rich blood from oxygen-poor blood. This separation allows these animals to maintain a high body temperature and a high level of activity.
• Snakes, on the other hand, have three-chambered hearts. A three-chambered heart is less efficient than a four-chambered heart, but it is sufficient for the needs of a snake. Snakes are cold-blooded animals and do not have the same energy demands as mammals and birds.

Thus, the right answer to this question is a snake.

The T wave represents the return of the ventricles from excited to normal state (repolarisation)