Final answer:
The correct statement about "A chantar m'er" is that it has no clearly articulated meter or rhythm but is sung in notes of more or less equal length (Option B).
Step-by-step explanation:
The statement that correctly identifies "A chantar m'er" is that the song features no clearly articulated meter or rhythm and is monophonic in texture.
This song, which is a troubadour song or chanson, is one of the few entire pieces of music that survive from that era and demonstrates the monophonic and secular qualities of much of the medieval music of its time.
The work is not in rondeau form, nor does it have a sacred theme intended for liturgical purposes as would be composed by Hildegard of Bingen or be in the style of Cyprien de Rore's motets.
It features the more complex use of polyphonic textures and harmonies, especially the use of the interval of the third.
Hence, the correct answer is Option B.