24 multiple-choice questions in College Board exam style. Each has four choices and a full explanation of why each option is right or wrong.
Read the question carefully before looking at the choices. Many APES questions have answers that look almost identical; small wording differences matter.
Don't confuse ozone depletion with the greenhouse effect. Different chemicals, different layers, different exam answers.
Remember CO2's two separate effects. The greenhouse effect (atmosphere) and ocean acidification (oceans) are distinct mechanisms.
Read the explanations even when you got it right. Each one teaches a small fact that often returns in a different form on the exam.