What defines a Perfect Authentic Cadence (PAC)?

A Perfect Authentic Cadence (PAC) is defined by a specific harmonic and melodic structure that provides a strong sense of resolution and closure in music. It occurs when there is a progression from the dominant chord (V) to the tonic chord (I). For the cadence to be classified as "perfect," both chords must be in root position, which means that the bass note of each chord is the root of that chord. Furthermore, the melodic line must culminate on the tonic note in the highest voice, typically the soprano.

This combination creates a definitive and satisfying endpoint in the music, making it one of the most conclusive cadences in tonal music. The emphasis on both the root position of the chords and the placement of the final melodic note being on the tonic is what distinguishes a PAC from other types of cadences.

In contrast, other options describe different types of chord progressions or cadences that do not meet these criteria, such as the use of inverted chords or resolutions that do not culminate on the tonic note. These variations would not convey the same strength of resolution that is characteristic of a Perfect Authentic Cadence.