A round is an example of Polyphonic music.
Not more than 4 in a measure, hope this helps !!
The best and most correct answer among the choices provided by the question is organum.
Organum, a preexistent chant is embellished by the addition of other voices singing different music. When music is made up of people singing or playing different lines at the same time, it is said to be polyphonic.
Hope my answer would be a great help for you.
MEAT HE WEIGHS MEAT BECAUSE HES A BUTCHER I GET IR HAHAHAH