Write a brief answer to the question given below.
 
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
 
a. The division between oxygenated and deoxygenated blood allows proper oxygen distribution in the body.
b. This feature is advantageous in animals having minimal energy requirements.
c. Mammals and birds require a constant supply of oxygen to obtain energy and to maintain their constant body temperature.