Which trumpet sounds a major 2nd lower than written?

The Bb trumpet is the correct choice because it is a transposing instrument that sounds a major second lower than written. When a musician plays a written C on the Bb trumpet, the pitch that is actually produced is a Bb, which is a whole step lower. This transposition is a fundamental characteristic of the Bb trumpet, making it a popular choice for concert band and jazz ensembles.

Other types of trumpets, such as the C trumpet, do not transpose; they sound at concert pitch. The D trumpet is a higher pitch instrument that sounds a whole step higher than the written note, while the Eb trumpet also transposes, but it sounds a minor sixth lower than the written note. Therefore, the Bb trumpet is specifically designed for the transposition of one whole step down, confirming its significance in various musical contexts.