Which is the common character between all the mammals?

Step-by-step solution

The most unique mammalian characteristic is the presence of milk-producing glands (mammary glands) by which the young ones are nourished. They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming, or flying. The skin of mammals is unique in possessing hair. External ears or pinnae are present. Different types of teeth are present in the jaw. The heart is four-chambered. The presence of seven cervical vertebrae. They are homoiothermic. Respiration is by lungs. Sexes are separate and f