What will happen when RTA comes back online?

During a recent OSPF election among three routers, RTA was elected the DR and RTB was
elected the BDR, as seen in the graphic. Assume that RTA fails, and that RTB takes the place of
the DR while RTC becomes the new BDR. What will happen when RTA comes back online?

A.
RTA will take the place of DR immediately upon establishing its adjacencies.

B.
RTA will take the place of DR only if RTB fails.

C.
RTA will take the place of DR only if both RTB and RTC fail.

D.
A new election will take place establishing an all new DR and BDR based on configured priority
levels and MAC addresses.

Explanation:
If a router with a higher priority value gets added to the network, it does not preempt the DR and
BDR. The only time a DR and BDR changes is if one of them is out of service. If the DR is out of
service, the BDR becomes the DR, and a new BDR is selected. If the BDR is out of service, a new

BDR is elected. In a multi-access network, the router that is powered on first will generally become
the DR, since the DR/BDR process is not pre-emptive.
Reference:: CCNP Self-Study Second Edition P.243