Which description fits brass instruments?

Brass instruments are categorized by their distinct construction and sound production method, which involves a cup-shaped mouthpiece connected to a series of metal tubing. This design allows the musician to create sound by buzzing their lips into the mouthpiece, which then resonates through the metal body of the instrument. The shape and length of the tubing, along with various valves or slides, enable players to adjust pitch and tone, contributing to the rich, powerful sound characteristic of brass instruments.

The other descriptions do not align with the fundamental nature of brass instruments: reed mouthpieces are associated with woodwinds, strung instruments pertain to the string family, and electronic instruments are distinctly categorized apart from acoustic brass instruments. Therefore, the description focusing on the cup-shaped mouthpiece and metal tubing precisely captures the essence of brass instruments.