The rate of gas exchange in mammals is maximized by an exceedingly high partial pressure of o2 in the blood. the opening of the larynx (voice box) into the trachea. an enormous surface area for gas exchange. the animals' small increase in size during inhalation. the production of mucus and surfactants.

Option C, an enormous surface area for gas exchange

Explanation:

The process of gas exchange in any mammal depends on following factors -  

a) Thin membrane of respiratory surfaces involved in gas exchange

b) High speed of diffusing gases

c) High Surface area  

d) Solubility (lipid solubility) of carbon dioxide and oxygen

The rate of diffusion of gas across a membrane is directly proportional to the surface area of the membrane through which diffusion is taking place. Thus, the higher the surface area, the higher is the gas exchange.  

Hence, option C is correct

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.