Ans- The primary function of blood is to regulate the internal environment in the body. It is because of the circulating blood that makes adaptability to changing conditions possible.Respiration- A constant supply of oxygen to all living cells in the body is vital, especially those of the brain, deprivation of which can cause unconsciousness and death.  Nutrition- The substances required for the nutrition of the cells in the body are transported via the blood. Carbohydrates, proteins, fats, minerals, salts. Vitamins and other substances pass through the blood plasma on their way to the tissues. Excretion- Blood is responsible for carrying the waste products to the excretory organs. Carbon dioxide is removed via the lungs while kidneys filter the blood for excessive water.Immunity - Cells of the blood are responsible to interact with the infectious agents, resist or destroy invading organisms and remove foreign and dead materials.Temperature regulationBlood Clotting