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.
Trace code carefully. Track each variable's value line by line, and watch loop bounds for off-by-one errors.
MOD is the remainder; binary search needs a sorted list. These come up often.
Think about efficiency, not just correctness: how does the number of steps grow with input size?
Read the explanations even when you got it right, and re-check AND vs. OR conditions.