During respiratory distress, infants and children are highly susceptible to hypoxia because their:

A. metabolic oxygen demand is doubled, compared to an adult's.
B. respiratory rate must remain faster than an adult's.
C. hemoglobin level is proportionately lower than an adult's.
D. functional residual capacity is larger than an adult's.

Answer: A. metabolic oxygen demand is doubled, compared to an adult's.