What must be done to fix this error?

Refer to the exhibit.

After configuring two interfaces on the HQ router, the network administrator notices an error
message. What must be done to fix this error?

A.
The serial interface must be configured first.

B.
The serial interface must use the address 192.168.1.2

C.
The subnet mask of the serial interface should be changed to 255.255.255.0

D.
The subnet mask of the FastEthernet interface should be changed to 255.255.255.240

E.
The address of the FastEthernet interface should be changed to 192.168.1.66

Explanation: