One-word substitution (vocabulary): Choose the correct term for “a person who insists on something (strict about rules or details).” Select the single best word that matches the definition exactly.

Reasoning through options Stickler — someone who insists on exactness and proper procedure; stickler for rules/details. Disciplinarian — enforces discipline (often authority figure); not necessarily an “insists on details” type. Instantaneous — adjective meaning immediate; not a person. Boaster — braggart; unrelated to insistence on rules.

Final Answer Stickler