Which Statement Regarding Microcirculatory Beds Is True

Which statement regarding microcirculatory beds is true?

A) Smooth muscles in the walls of arterioles are responsible for vasoconstriction and vasodilation.
B) Anastomoses are the one possible path from an arteriole to a venule.
C) The walls of capillaries consist of vascular endothelium and a smooth muscle layer.
D) Venules and arterioles are the preeminent sites of O₂ and water exchange.