Read this excerpt from "A Student's Guide to Global Climate Change." You probably know someone with asthma, or maybe you have this condition yourself. Certain kinds of air pollutants, like ozone, can make asthma and other lung conditions worse. Ozone found high in the atmosphere is called "good ozone" because it protects life on Earth from the sun's harmful ultraviolet rays. Ozone can also be found close to the surface of the Earth, where it is considered “bad ozone” because it's the main ingredient of smog and is harmful for people to breathe. Bad ozone is created from pollutants that go through chemical reactions in the atmosphere. Climate change is likely to increase the amount of bad ozone in the air because more ozone is created when the temperature is warm.

Which best states the author’s purpose in writing the paragraph?

to compare and contrast “good” and “bad” ozone layers
to inform readers about the negative effects of air pollution on life
to increase awareness of asthma and other lung conditions
to list the steps involved in creating a “bad” layer of ozone