Why is it important to remove harmful materials from waste before putting the waste in the environment?

The excerpt above is from page 21 of harry potter and the sorcerers stone by j.k rowling. which passage represents a

Suppose you need to verify how to correctly use commas. you open your english textbook and scan the chapter titles. in which one would you most likely find the information you need? ; ; ; ; that's the ? im having truble with

What is the reasoning in this argument?