where should the root guard feature be configured to preserve SW3 as a root bridge?

Refer to the exhibit.

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

A.
SW4 Gi0/0 interface.

B.
Sw3 Gi0/0 interface.

C.
Sw2 Gi0/1 interface.

D.
SW2 Gi0/1 and SW3 Gi0/1