what must the administrator do to enable CDP to exchange information between R1 and R2?

Refer to the exhibit.

The two routers have had their startup configurations cleared and have been restarted. At a
minimum, what must the administrator do to enable CDP to exchange information between R1 and
R2?

A.
Configure the router with the cdp enable command.

B.
Enter no shutdown commands on the R1 and R2 fa0/1 interfaces.

C.
Configure IP addressing and no shutdown commands on both the R1 and R2 fa0/1 interfaces.

D.
Configure IP addressing and no shutdown commands on either of the R1 or R2 fa0/1
interfaces.

Explanation:
If the shut down commands are not entered, then CDP can exchange information
between the two routers, else it would fail.