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

Options

A. c: arterial capillary passes oxygen to tissues
B. a : alveolar cavity main site of exchange of respiratory gases
C. d: capillary wall - exchange of `O_(2)` and CO(2)`takes place here
D. b: red blood cell transport of `co_(2)` mainly

Answer

B