Why Do Synthetic Chemicals and Metals Tend to Bioaccumulate So

Why do synthetic chemicals and metals tend to bioaccumulate so readily?

A) These substances are so rare in natural environments that living organisms have developed very efficient methods of collecting them.
B) Natural reservoirs are so large that when expressed as a concentration putting the same amount into an organism will always produce an elevated value.
C) Synthetic chemicals often have no nutritional value, so they are simply stored in the body and passed on when an organism is eaten.
D) They are stable chemicals and are accumulated in the cells of organisms more rapidly than they can be removed.