The organ ‘A’ of a person has been damaged completely due to a poisonous waste material "B' has started accumulation in his blood, making it dirty. In order to save this person's life, the blood from an artery in the person's arm is made to flow into long tubes made of substance 'E'which are kept in coiled form in a tank containing solution "F". This solution contains three materials 'G', 'H' and 'l' similar proportions to those in normal blood. As the person's blood passes through long tubes of substance 'E', most if the wastes present in it go into solution 'F'. The clean blood is then put back into a vein in the person for circulation
What is organ A?