Answer:
The excretory system is a passive biological system that removes excess, unnecessary materials from the body fluids of an organism, so as to help maintain internal chemical homeostasis and prevent damage to the body.
Explanation:
neither agriculture nor medicine because agriculture is about practice of farming, including cultivation of the soil for the growing of crops and the rearing of animals to provide food, wool, and other products. And I hope you know what medicine is about so ya it's the last one.
Its like the circle of life kind of. Like the fish are food for the sharks and bigger fish and smaller fish for the medium fish and algae for the little fish.