What distinguishes an authentic cadence from a plagal cadence?

The correct choice highlights the fundamental difference in the resolution of cadences. An authentic cadence is characterized by its movement from the dominant chord (the fifth scale degree) to the tonic chord (the first scale degree). This strong resolution is a defining feature of authentic cadences and is crucial in establishing the key of the piece clearly.

In contrast, a plagal cadence moves from the subdominant chord (the fourth scale degree) to the tonic. Often referred to as the "Amen cadence" because of its frequent use at the end of hymns, it has a softer and more conclusive sound compared to the stronger resolution of the authentic cadence.

Understanding these progressions helps musicians and composers recognize how different cadences function within a key, creating distinct emotional impacts and providing structural closure in music.