The kidneys are important organ in excretory system. Kidneys are located above renal cells in the level of organization that describe the excretory system. What does this show about the relationship between renal cells and the kidneys?

A. Renal cells are made up of many tissues.

B. Kidneys are made up of many renal cells.

C. Kidneys are less complex than renal cells.

D. Renal cells are less important than kidneys.