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 on Catalyst R so that R2 becomes the root port on Catalyst D for VLAN 2.