Hair occur in all mammals except those of (a) rodentia (b) chiroptera (c) primata (d) cetacea.
Option D Order Cetacea includes whales, dolphins and porpoises. These are the most highly modified mammals. They have a fishlike body with smooth, hairless skin devoid of sweat and oil glands, far posterior nares, small eyes, minute ear openings without pinnae, paddlelike forelimbs, no hindlimbs, abdominal testes and flattened tail ending in two horizontal flaps or flukes.
