<prompt> Respiratory quotient of the brain is?0.6-0.70.7-0.80.8-0.90.9-1.0  <response>: Ans. D 0.9-1.0 Respiratory quotient RQ is the ratio in the steady state of the volume of carbon dioxide produced to the volume of oxygen consumed per unit time. RQ of the brain is 0.97-0.99; this is because the principal fuel for the brain is carbohydrates. 