Penguins are among the most social of all birds. All species are colonial. Penguins have a thick layer of insulating feathers that keeps them warm in water (heat loss in water is much greater than in air). They often huddle together to keep warm and rotate positions to make sure that each penguin gets a turn in the center of the heat pack. Penguins either waddle on their feet or slide on their bellies across the snow, which conserves energy while moving quickly. They also jump with both feet together if they want to move more quickly or cross steep or rocky terrain. Thus, the correct answer is option C.