Which statement best describes the ability of a wireless client to access and transmit a data frame to an AP?

A.	The client listens to the media until polled by the AP using PCF to send its data.
B.	The client listens to the media until a data frame is finished, at which time it transmits, unless a collision of data frames has occurred.
C.	The client uses random countdown timers to start the transmission of a data frame.
D.	The client listens to the media and countdown timers to start the transmission of a data frame.