Prior to 802.1w， Cisco implemented a number of proprietary enhancements to 802.1D to improve convergence in a Layer 2 network. Which statement is correct？（）

• A、Only UplinkFast and BackboneFast are specified in 802.1w； PortFast must be manually configured.
• B、Only PortFast is specified in 802.1w； UplinkFast and BackboneFast must be manually configured.
• C、None of the proprietary Cisco enhancements are specified in 802.1w.
• D、PortFast， UplinkFast， and BackboneFast are specified in 802.1w.