The digestive system:
A. mechanically and chemically assembles food from absorbed nutrients.
B. sends cellular debris to lysosomes.
C. circulates nutrients throughout the body.
D. mechanically and chemically breaks down food for nutrient absorption.
E. builds macromolecules for tissue repair.

The tragedy of commons, is when somebody acts individually, and not in the way a group of people wants. You could say it's when they act out of common sense in a way, and the only thing that represents that is the first option.

Not everybody likes the idea of pumping and other gasses in to the atmosphere, in fact, nobody should. But there are some people that benefit from that (owners, managers from factories and their associates).

Hope it helped,

BioTeacher101