The thin, narrow structure of the capillaries is well-suited to their function because the capillaries
a) only carry the liquid portion of blood
b) transport substances directly to the body cells
c) require only a small amount of oxygen to function
d) have the opposite function of arteries and veins

The correct option is B. The capillaries transport substances directly to the body cells and their structure enables reduction of diffusion distance.

20 times a minute is usually the average respritory rate of an adult. additionally the patient is breathing on his own, is clearly maintaining his airway, and is intaking a sufficient amount of air. you shouldn't use a bag valve mask, cpap, or other form of positive pressure ventilation, unless the patient has lost control of his airway, and is not breathing (apneic) or has rapid breathing or slow and shallow respirations. this patient would most likely and should be put on an non-rebreather mask or nrb attached to 100% high flow oxygen at 15 l/min. don't use a nasal cannula, as the amount of oxygen it provides is limited with a rate of 6 l/min.