(i) Why is respiratory pigment needed in multicellular organisms with large body size?
(ii) Give reasons for the following:
(a) Rings of cartilage are present in the throat.
(b) Lungs always contain a residual volume of air.
(c) The diaphragm flattens and ribs are lifted up when we breathe in.
(d) Walls of alveoli contain an extensive network of blood vessels.