Which set of instruments is included in the brass category?

The brass category comprises instruments that produce sound through the vibration of air in a tubular structure, typically made of metal. The correct answer, featuring the trumpet, horn, trombone, and tuba, reflects this characteristic. Each of these instruments utilizes a mouthpiece where the player buzzes their lips, causing the air column within the instrument to resonate, creating sound.

This grouping not only identifies instruments that belong to the brass family but also highlights their shared construction materials and playing techniques. In contrast, the other options contain instruments from different families: woodwind for the first option (flute, oboe, clarinet, bassoon), strings for the third option (violin, viola, cello, bass), and a combination of percussion and keyboard for the fourth option (piano, drums, guitar, saxophone). These distinctions underscore the classification of instruments based on how they produce sound and their physical characteristics.