Sympathetic nervous system stimulation causes arrector pili contraction Steps:

• Identify hair erector muscles as arrector pili, controlled by sympathetic nerves.
• Recall triggers: cold exposure activates via thermoreceptors; adrenaline release from fear/stress stimulates directly.
• Match to options: assume 1 is cold exposure, 4 is fear/emotion based on standard biology contexts.
• Eliminate pairs without both triggers.

Why B is correct:

• Combines cold (1) and fear (4), both proven sympathetic activators per autonomic physiology.

Why the others are wrong:

• A: Lacks fear trigger; 3 likely unrelated (e.g., heat).
• C: Misses cold; 2 probably non-stimulant (e.g., relaxation).
• D: Omits cold; pairs weak trigger with irrelevant.

Not enough information on exact actions 1–4 for full certainty. Final answer: B