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 bioaccumulation with biomagnification. One happens within an organism, the other happens across trophic levels.
Know the three sewage treatment stages in order. Primary, then secondary, then tertiary: each removes something different.
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.