The figure given below shows a small part of human lung where exchange of gas 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.
(a) A - Alveolar cavity - main site of exchange of respiratory gases
(b) D - Capillary wall - exchange of gases takes place here
(c) B - Red blood cell - transport of mainly haemoglobin
(d) C - Arterial capillary - passes oxygen to tissues
