Which standard supports multiple instances of spanning tree？（）

A.Loop guard can be used with root guard simultaneously on the same port on the same VLAN while UDLD cannot.
B.UDLD protects against STP failures caused by cabling problems that create one-way links.
C.Loop guard detects and protects against duplicate packets being received and transmitted on different ports.
D.UDLD protects against unidirectional cabling problems on copper and fiber media.
E.Loop guard protects against STP failures caused by problems that result in the loss of BPDUs from a designated switch port.

A.Increase the root bridge priority （increasing the numerical priority number） for VLAN 2 on Catalyst D so that port D2 becomes the root port on Catalyst D for VLAN 2
B.Decrease the port priority on R2 for VLAN 2 on Catalyst R so that port D1 will be blocked for VLAN 2 and port D2 will remain blocked for VLAN 1
C.Decrease the path cost on R2 on Catalyst R for VLAN 2 so that port D1 will be blocked for VLAN 2 and port D2 will remain blocked for VLAN 1
D.Increase the root bridge priority （decreasing the numerical priority number） for VLAN 2 onCatalyst R so that R2 becomes the root port on Catalyst D for VLAN 2