Concept:Aged red blood cells are removed and destroyed by organs of the reticuloendothelial system.Explanation:Erythrocytes have a lifespan of about 120 days.Worn-out red blood cells are broken down mainly in the spleen and liver.The liver also recycles iron and bilirubin from destroyed erythrocytes.Since the spleen is not listed among the options, the liver is the correct organ.Answer:B. liver