If SW4 is sending superior BPDUs, where should the root guard feature be configured to preserve SW3 as a root bridge? 

Answer options:

A. SW4 Gi0/0 interface.
B. Sw3 Gi0/0 interface.
C. Sw2 Gi0/1 interface.
D. SW2 Gi0/1 and SW3 Gi0/1

C