20 points!!!!!
In general, how do veins differ in structure from capillaries and arteries?
A Veins have more smooth muscle tissue than arteries and capillaries.
B Veins appear rounder in a cross section than arteries and capillaries.
C Veins have valves which are absent in arteries and capillaries.
D Veins have thinner inner walls than arteries and capillaries.