Two departments A and B have been added into a consolidated billing organization. Department A has 5 reserved RDS instances with DB Engine as MySQL. During one particular hour, department A used three DB Instances, and department B used two RDS instances for a total of 5 DB Instances on the consolidated bill. How should the RDS instances in department B be configured so that all five instances are charged as Reserved DB Instances?

Answer options:

A.Department B should launch DB instances in the same region as Reserved Instance in department A.B.The DB engine in Department B should be MySQL.
C.The DB Instance Class should be the same in both departments such as m1.large.
D.The deployment type such as Multi-AZ should be the same in both department A and department
B.E.All the above are needed.

Correct Answer E
In order to receive the cost-benefit from Reserved DB Instances, all the attributes of DB Instances (DB Engine, DB Instance class, Deployment type, and License Model) in another account should match the attributes of the Reserved DB Instances.
Option A & D are all required, and do find the reference in the following link.
Option E is CORRECT: Because all of the other options are needed. The reference is in https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/consolidatedbilling-other.html.