A premature baby in critical condition with high blood pressure in his lungs is administered a blend of nitric oxide (a vasodilator)and oxygen to reduce his blood pressure.Nitric oxide reduces blood pressure by

A) constricting the muscle cells around arterioles.
B) reducing the heart rate.
C) blocking the formation of new capillaries.
D) relaxing the muscle cells around arterioles.
E) increasing the formation of capillaries.