35 multiple-choice questions in College Board exam style. Each has four choices and a full explanation of why each option is right or wrong.
Recognize the form first: geometric, p-series, alternating, or ratio-test friendly.
aₙ → 0 is necessary, not sufficient: the harmonic series diverges.
For power series, use the ratio test for R, then test the endpoints.
Read the explanations even when you got it right, and memorize the series for eˣ, sin x, cos x, 1/(1−x).