What provides harmonic support in the "Marriage Celebration Song"?

In the context of the "Marriage Celebration Song," the correct choice is that heterophony provides harmonic support. Heterophony is a musical texture where multiple voices or instruments simultaneously perform variations of the same melody. This creates a rich tapestry of sound that adds depth and complexity to the music, which is particularly effective in celebratory or communal songs like those often performed during weddings.

In this song, different performers may embellish or modify the main melody, resulting in a layered effect that enhances the harmonic richness. This is distinct from other textures, such as monophony, where only a single melody is presented without harmonic support, and counterpoint, which involves the interaction of two or more independent melodies. Harmony on its own typically refers to the vertical combination of notes played simultaneously, rather than the interweaving of a single melody with variations. Therefore, in this instance, heterophony is the most fitting description for the harmonic support in the "Marriage Celebration Song."