Final answer:
The best description of a motet is a religious choral composition, predominantly polyphonic and without instrumental accompaniment, evolving from the medieval period into the Renaissance.
Step-by-step explanation:
The phrase that best describes a motet is d. Religious choral composition. A motet is a polyphonic vocal genre frequently in sacred, or religious, contexts. It became prevalent during the medieval period and continued well into the Renaissance. Core characteristics of the motet include its use of a sacred Latin text and its performance by a choir, typically without instrumental accompaniment.
Motets were developed in the high medieval era and became a principal liturgical form alongside masses. As the Renaissance progressed, motets evolved, with composers incorporating elements of secular genres, such as the madrigal, into this traditionally sacred form. Despite these influences, the motet remained primarily a religious choral composition throughout the Renaissance.