Passage Summary: Cat allergies are caused by different proteins for different people, and since all cats have these proteins, every cat can cause an allergy, even if it doesn't affect everyone.

Reasoning: Allergies are triggered by specific proteins in cat secretions, but the specific proteins vary by person; because all cats produce these secretions, no cat is entirely non-allergenic, though a specific cat may not trigger every allergic person.

Analysis: Treat these premises as absolute facts. The stimulus establishes that while all cats produce allergenic proteins, the specific protein that triggers a reaction varies from person to person. This creates a scenario where a person might be fine around one cat but react to another, yet no cat can be labeled 'allergy-proof' for the entire population. Look for an answer choice that synthesizes these facts, likely concluding that an individual's reaction depends on the specific proteins a particular cat produces.