A user has attached one RDS security group with 5 RDS instances. The user has changed the ingress rule for the security
group. What will be the initial status of the ingress rule?

A.
Approving

B.
Implementing

C.
Authorizing

D.
It is not possible to assign a single group to multiple DB instances

Explanation:
When the user makes any changes to the RDS security group the rule status will be authorizing for some time until the
changes are applied to all instances that the group is connected with. Once the changes are propagated the rule status
will change to authorized.
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_WorkingWithSecurityGroups.html