Why do organs need a constant supply of blood?
a. to continually clean the organs, blood must constantly pass through them.
b. to continually the cells within the organs change into new types of cells
c. to continually produce energy, your organs need oxygen and the oxygen is
carried in your red blood cells.
d. none of the above
only answer if you know the actually answer

c. In order to get required amount of oxygen, the organs require constant supply of blood.

The major components of the organ system is nothing but the organs. If they perform well, then only the entire organ system functions properly in turn this facilitates normal functioning of the body.  

For proper functioning of the organs, oxygen act as key supplements. This oxygen is carried out throughout the body the blood. Without the blood the organ cannot get sufficient oxygen required for their metabolic activity.

Thus, constant supply of blood to the organ is required for the proper functioning of the body.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.

digestion

it excretes wastes