Q4. The figure given below shows a small part of human lung where exchange of gases takes place. In which one of the options given below, the one part A, B, C or D is correctly identified along with its function? (1) A. Alveolar cavity - main site of exchange of respiratory gases. 11 B. Arterial capillary - passes oxygen to tissues D co C. Red blood cell - transport of CO, mainly நடுந் A B. so D. Capillary wall - exchange of O, and CO, takes place here