【单选题】
IEEE 802.1w is a Rapid Spanning Tree Protocol （RSTP） that can be seen as an evolution of the 802.1 standard. What are the port roles described by 802.1w？（）
A、root port，designated port，alternate port，backup port，and disabled
B、standby port，alternate port，root port，and disabled
C、standby port，designated port，backup port，and disabled
D、root port，designated port，alternate port，and standby port
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