premise: A train makes five trips around a loop through five stations—P, Q, R, S, and T, in that order—stopping at exactly three of the stations on each trip. The train must conform to the following conditions: The train stops at any given station on exactly three trips, but not on three consecutive trips. The train stops at any given station at least once in any two consecutive trips. Which one of the following could be the list of stations at which the train stops on the first two trips?
hypothesis: first trip: Q, R, S; second trip: P, Q, S