Ace the AP Psychology Test 2026 – Unlock Your Mind’s Potential!

An unconditioned stimulus (UCS) is something that naturally and automatically triggers a response without any prior conditioning. Option A is incorrect because a learned response to a neutral stimulus is a conditioned response, not an unconditioned stimulus. Option B is incorrect because it says "occurs" instead of "triggers" and does not mention the stimulus. Option D is incorrect because it describes a conditioned response, not an unconditioned stimulus. Option C is the correct answer because it accurately describes an unconditioned stimulus triggering a response without any prior conditioning.