The correct answer is (a). Desert dwelling animals are called xeric animals. Xeric animals are adapted to living in dry, arid environments. They have a number of adaptations that help them to conserve water, such as thick fur or feathers, and they often have a nocturnal lifestyle to avoid the heat of the day.
(b) Arboreal animals are animals that live in trees. They have a number of adaptations that help them to climb trees, such as sharp claws and strong limbs.
(c) Fossorial animals are animals that live underground. They have a number of adaptations that help them to dig, such as strong claws and a long snout.
(d) Aquatic animals are animals that live in water. They have a number of adaptations that help them to breathe underwater, such as gills or a swim bladder.