The correct option is B Nephron
The functional unit of the kidney that serves to remove waste from the body is the nephron. Each kidney is composed of over one million nephrons that dot the renal cortex, giving it a granular appearance when sectioned sagittally (from front to rear). There are two types of nephrons: cortical nephrons (85 percent), which are deep in the renal cortex; and juxtamedullary nephrons (15 percent), which lie in the renal cortex close to the renal medulla.