Answer:
a. they will eventually be excreted by digestive system.
Explanation:
The average life span of healthy red blood cells (RBCs) is 120 days. After 120 days, RBCs are transported to spleen which is also known as graveyard of RBCs. In the spleen RBCs are broken into iron and bile pigment by several digesting enzymes. The iron is transported back to the red bone marrow to use it for the formation of new RBCs. The non-iron portion of heme goes through a series of chemical conversions that eventually end up in the large intestine which is what gives feces its characteristic brown color.
