Catalyst 3500 (Catalyst OS (CatOS)系统）中配置UnlinkFast生成树可选功能的命令格式( )。

A) spanning-tree uplinkfast<cr>

B) set spantree uplinkfast enable<cr>

C) spanning-tree uplinkfast max-update-rate<0-32000$amp;>amp;$lt;or>

D) spanning-tree vlan<vlan>root primary