Explaining every distractor

Explaining wrong options is the highest-yield review. For each option you eliminated, complete the sentence: "A student picks this if they believe ___ , but actually ___ ." Two examples:

• Option "8" for f(4) where f(n) = f(n-1) + n, f(0) = 1: picked by treating the base case as 0 (or summing 1+2+3 without +4 … no — by forgetting the base case returns 1, not 0). Actually the chain is f(0)=1 → 1+1=2 → 2+2=4 → 4+3=7 → 7+4=11.
• Option "[b, d]" for remove-while-iterating over [a,b,c,d,e] removing even indices: picked by forgetting that remove shifts later elements left, so the next comparison lands on a different element. Actually the survivor set is [b, c, e].

Twenty of these and distractors stop fooling you — you recognize the misconception in the option and reverse-engineer which trap it is. That is the intended exam use of elimination: not "which looks right" but "which error does each wrong answer assume."