Prove that the whale is a mammal, not a fish.

A whale breathes in its lungs, not its gills. The body of the whale is covered in skin, not scales. The whale carries the cubs and feeds them with milk. Whales have no fins. Their flippers are mutated limbs.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.