what is the recommended DTIM value of the WLAN for VoWLAN devices?

When using simultaneous voice and multicast on a single WLAN and RF band, what is the recommended DTIM value of the WLAN for VoWLAN devices?

A.
DTIM = 1

B.
DTIM = 2

C.
DTIM = 3

D.
DTIM = 4