What is the best practice for configuring data rates for an 802.11g VoWLAN deployment?

What is the best practice for configuring data rates for an 802.11g VoWLAN deployment?

A.
Configure mandatory data rates of 12 and 54 Mb/s. Disable data rates below 6 Mb/s, and
configure all other data rates as supported.

B.
Configure a mandatory data rate of 6 Mb/s. Disable data rates below 6 Mb/s, and configure all
other data rates as supported.

C.
Configure a mandatory data rate of 11 Mb/s. Disable data rates below 11 Mb/s, and configure
all other data rates as supported.

D.
Configure a mandatory data rate of 12 Mb/s. Disable data rates below 12 Mb/s, and configure
all other data rates as supported.

Explanation: