What of the following is a classical accompaniment style based on triads?

A classical accompaniment style based on triads is known as "block chords." In this style, chords are played in a solid manner, meaning all the notes of the triad are struck simultaneously or in a rhythmic pattern. This creates a harmonic foundation for melodies, often found in piano compositions and Classical Music settings. Other related styles include arpeggiOS, where the notes of the triad are played in succession rather than together.