The Company network utilizes the Multiple-instance Spanning Tree protocol in its switched LAN. Which three statements about the MST protocol （IEEE 802.1S） are true？ （）

A. To verify the MST configuration， the show pending command can be used in MST configuration mode.
B. When RSTP and MSTP are configured； UplinkFast and BackboneFast must also be enabled.
C. All switches in the same MST region must have the same VLAN-to-instance mapping， but different configuration revision numbers.
D. All switches in an MST region， except distribution layer switches， should have their priority lowered from the default value 32768.
E. An MST region is a group of MST switches that appear as a single virtual bridge to adjacent CST and MST regions.
F. Enabling MST with the "spanning-tree modemst" global configuration command also enables RST