Which of the following accurately describes the pipa's structure?

The pipa is a traditional Chinese string instrument, and option A accurately describes its structure by highlighting two key characteristics: the curved body and the bent neck. The pipa is known for its almond-shaped, rounded body which contributes to its resonance, and its neck is bent, allowing for a unique range of pitches when played. This design is essential for producing the distinctive sound and tonal qualities associated with the pipa, making it a staple in Chinese music.

The other descriptions do not fit the pipa's structure. It is not a wind instrument, as it is a plucked string instrument. Additionally, it does not lack strings, nor does it have sliding features typical of sliding string instruments like the slide guitar or trombone. Lastly, while percussion instruments can be complex, the pipa does not have a percussion mechanism but instead relies on its strings and the plucking technique to create sound. Thus, option A is the only description that accurately captures the essence of the pipa's construction.