Final answer:
The biggest animal in the world is the blue whale, significantly larger than elephants, giraffes, and chickens. It is the largest living vertebrate known, reaching lengths of up to 110 feet.
Step-by-step explanation:
The Largest Animal in the World
The biggest animal in the world is the blue whale (A). Blue whales are marine mammals and are known to be the largest living vertebrates, reaching an astounding length of up to 110 feet. These magnificent creatures dwarf other large animals such as the elephant, giraffe, and are certainly much larger than a chicken. The size of the blue whale is even more impressive when compared to the smallest whale species, Hector's dolphin, which measures about 5 feet in length. The vertebrates form a broad group within the animal kingdom, which also includes other large mammals like elephants and giraffes, but none match the sheer size of the blue whale.
As part of the Classification of Vertebrates, these animals are also grouped alongside others such as rabbits, mice, sea cows, horses, goats, zebras, deer, elk, hippopotami, kangaroos, and monkeys, which all come under the umbrella of vertebrates due to possessing a backbone.