The individual rhythms of polyrhythmic music are a. identical. b. independent and contrasting. c. played only once. d. created by chance.

I believe the correct answer is B. independent and contrasting.

The polyrhythm is the musical technique which uses two or more conflicting rhythms simultaneously. These rhythms are not deriving from one another, which means that they are not simple manifestations of the same meter. Polyrhythms are sometimes called "cross rhythms" because this musical technique that involves playing two or more different rhythms at the same time.