A. A WLAN RF is a full duplex, contention free medium where each client transmits on a separate channel.

B. A WLAN RF is a half-duplex, shared medium where 802.11 stations contend with each other for access.

C. A WLAN RF is a half-duplex, contention-free medium where the access point polls each station in turn.

D. A WLAN RF is a full-duplex, contention-free medium where 802.11 stations can transmit and receive at the same time.