The correct option is B 2, 1, 3
As blood passes through the lungs, the haemoglobin picks up oxygen because of the increased oxygen pressure in the capillaries of the lungs, and can then release this oxygen to body cells where the oxygen pressure in the tissues is lower. In addition, the red blood cells can pick up the waste product, carbon dioxide, some of which is carried by the haemoglobin (at a different site from where it carries the oxygen), while the rest is dissolved in the plasma. Thus, option C is correct.