They carry about 20-25 percent of CO₂.

They transport 99.5 percent of O₂.

They transport about 80 percent oxygen only and the rest 20 percent of it is transported in dissolved state in blood plasma

They do not carry CO₂ at all.

has only 2 protein subunits instead of 4

has a higher affinity for oxygen than that of an adult

has a lower affinity for oxygen than that of the adult

its affinity for oxygen is the same as that of an adult.

Inspiratory reserve volume plus expiratory reserve volume

Total lung capacity minus residual volume

Inspiratory reserve volum plus tidal volume

Total lung capacity minus expiratory reserve volume

The principle of countercurrent flow facilitates efficient respiration in gills of fishes.

The residual air in lungs slightly decreases the efficiency of respiration in mammals.

The presence of non-respiratory air sacs, increases the efficiency of respiration in birds.

In insects, circulating body fluids serve to distribute oxygen to tissues.