What method is used in an IEEE 802.11 WLAN to configure a QoS AP to deliver queued frames to a QoS STA during an unscheduled service period?

A.
The QoS STA’s client utility’s WMM access categories are manually configured by an administrator

B.
A QoS STA sends a TSPEC Request Frame to the QoS AP specifying its traffic flow requirements before using Power Management features.

C.
A QoS STA sends a (Re)Association frame to the QoS AP with the U-APSD Flag subfields set to 1.

D.
The WLAN controller’s WMM access categories are manually configured by an administrator.