A city issues three types of parking permits: resident, visitor, and commercial. Every commercial permit allows parking in loading zones. No visitor permit allows parking in loading zones. Some resident permits allow parking in loading zones, and some do not. Permit A allows parking in loading zones. Permit B is a visitor permit. Permit C is a commercial permit. Permit D is a resident permit. Each permit is exactly one type, and the only types are resident, visitor, and commercial.
Which one of the following can be properly inferred from the statements above?
- Permit A is not a visitor permit. (correct answer)
- Permit D allows parking in loading zones.
- Permit A is a commercial permit.
- Permit B does not allow parking in loading zones.
- Permit C is not a resident permit.
Explanation: In this inference question, the key facts are commercial → allows loading, visitor → not allows loading, some residents allow loading and some don't, A allows loading, B visitor, C commercial, D resident, each one type. Must-be-true statements are those entailed without assumptions. A allows loading and visitor → not allows yield, by contrapositive, allows → not visitor, guaranteeing choice A. A tempting wrong answer like C (A commercial) might seem plausible since commercial allows loading, but A could be a resident that allows it, so not forced. Correct inferences cannot require assumptions and must use logical tools like contrapositives directly from the facts.