B(i): the picture shows that the diaphragm is in its dome shape. Therefore, we can conclude that the person is undergoing the process of exhalation.
C: When diaphragm is not functioning, it reduces the efficiency of gases exchange.
D(i): gas exchange releases carbon dioxide, which is toxic to our body, into the air.
D(ii): the alveoli are moist for gas to dissolved, they are one cell wall thick that leads to efficiency of gases exchange, and they have large surface area to allow more diffusion to take place.