It was hypothesized that the decrease in blood flow to the skin resulted from a change in the activity of the sympathetic nerves to the skin. Which of the following observations would support this hypothesis?
O A change in the norepinephrine content of blood draining from the skin
O In vitro contraction of the smooth muscle in skin blood vessels in response to acetylcholine
O A lack of epinephrine receptors in skin blood vessels
O In vivo dilation of the skin blood vessels