Fact 1: Organs of excretion make up the excretory system.

Fact 2: Excretion begins with the kidneys.

Given the two facts above, answer the question "Kidneys are a part of what system?" with the following options: 
- allow growth
 - excretory
 - respiratory
 - organ
 - complex
 - storing water
 - endocrine
 - circulatory


 

  excretory       