Correct Option: D

Mammals are members of class Mammalia, airbreathing vertebrate animals characterized by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young. Most mammals also possess sweat glands and specialized teeth. The largest group of mammals, the placentals, have a placenta which feeds the offspring during gestation. Among the mammals, pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, sheep, goats belong to Order Artiodactyla; Order Cetacea: whales, dolphins and porpoises; etc. Mammals range in size from the 30–40 millimeter (1to 1.5-inch) bumblebee bat to the 33-meter (108foot) blue whale.