The correct answer is (a), shark. Sharks have a unique circulatory system that includes two separate pumps: a systemic heart and a branchial heart. The systemic heart pumps blood to the rest of the body, while the branchial heart pumps blood to the gills. This system allows sharks to maintain a high metabolic rate and survive in cold water.
Blue whales (b) have a single heart, as do elephants (c) and octopuses (d). Blue whales are the largest animals on Earth, and their hearts are the size of a small car. Elephants have the largest hearts of any land animal, and their hearts weigh up to 25 pounds. Octopuses have three hearts, but they are not the same as the hearts of sharks. The hearts of octopuses are used to pump blood to their gills, arms, and other organs.
In conclusion, the only animal that has three hearts and blue blood is the shark.