Which command will ensure that External_B will be the primary router for traffic using the
gateway address of 172.16.15.20?

A.
On External_B add the command standby 1 priority 80.

B.
On External_A add the command standby 1 priority 110.

C.
On External_A add the command standby 1 priority 80.

D.
On External_B remove the command standby 1 preempt