Correct option is 'B'.
Diffusion of dissolved gases because diffusion takes place in alveoli between walls of alveoli and endothelium. Diffusion is the process in which exchange of gases takes place. This process takes place without the expenditure of energy.
Active transport takes place in the plasma membrane with the expenditure of energy.
Osmosis is the process in which exchange of materials takes place through semi-permeable membrane.
