What would happen to an RDS (Relational Database Service) multi-Availability Zone deployment of the primary OB
instance fails?

A.
The IP of the primary DB instance is switched to the standby OB instance

B.
The RDS (Relational Database Service) DB instance reboots

C.
A new DB instance is created in the standby availability zone

D.
The canonical name record (CNAME) is changed from primary to standby

Explanation:
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html
Failover Process for Amazon RDS:
In the event of a planned or unplanned outage of your DB instance, Amazon RDS automatically switches to a standby
replica in another Availability Zone if you have enabled Multi-AZ. The time it takes for the failover to complete depends
on the database activity and other conditions at the time the primary DB instance became unavailable.
The failover mechanism automatically changes the DNS record of the DB instance to point to the standby DB instance.
As a result, you will need to re-establish any existing connections to your DB instance.