The young orchestral conductor Sabado Domingo is a true prodigy, able to recognize when any single instrument in his orchestra is even a bit out of tune. In a recent test, an orchestra played a hundred selections from different well-known classical pieces; in approximately half of the selections, exactly one instrument would be played slightly out of tune. In every instance in which an instrument was played out of tune, Domingo pointed out that the orchestra was out of tune, and correctly identified the instrument at fault. Which of the following, if true, most strongly supports the conclusion of the argument above? ['During the test, the orchestra was arranged in a traditional arrangement, similar to the arrangement in which they would be seated in a classical concert.', 'Because the test was performed in an empty concert hall, the acoustics of the concert hall differed somewhat from those of a concert hall populated by an audience.', 'The instruments played out of tune were all played at a pitch exactly one half-step lower than the true pitch.', "Domingo did not mistakenly label any of the orchestra's in-tune performances as out of tune."]