What is an appropriate configuration for a highly available database architecture?

A client application requires operating system privileges on a relational database server.

What is an appropriate configuration for a highly available database architecture?
A . A standalone Amazon EC2 instance
B . Amazon RDS in a Multi-AZ configuration
C . Amazon EC2 instances in a replication configuration utilizing a single Availability Zone
D . Amazon EC2 instances in a replication configuration utilizing two different Availability Zones

Answer: D

Explanation:

http://docs.aws.amazon.com/AWSEC2/Iatest/UserGuide/using-regions-avaiIabiIity-zones.htmI