The correct answer is option 2. Blubber refers to a layer of thick fat that is found in marine mammals such as whales, seals, and walruses. This layer of fat is important for these animals as it provides insulation, buoyancy, and energy storage. Blubber helps to keep these mammals warm in cold water and also helps them to float. It is made up of adipose tissue, which is a specialized type of connective tissue that contains a high amount of stored fat. This fat layer can vary in thickness depending on the species, location, and season. Blubber is an essential adaptation for these marine mammals, allowing them to survive in their cold aquatic environments.