Which of the following architectural choices should you make?

You have a web application running on six Amazon EC2 instances, consuming about 45% of resources on each instance. You are using auto-scaling to make sure that six instances are running at all times.

The number of requests this application processes is consistent and does not experience spikes. The application is critical to your business and you want high availability at all times. You want the load to be distributed evenly between all instances. You also want to use the same Amazon Machine Image (AMI) for all instances.

Which of the following architectural choices should you make?
A . Deploy 6 EC2 instances in one availability zone and use Amazon Elastic Load Balancer.
B . Deploy 3 EC2 instances in one region and 3 in another region and use Amazon Elastic Load Balancer.
C . Deploy 3 EC2 instances in one availability zone and 3 in another availability zone and use Amazon Elastic Load Balancer.
D . Deploy 2 EC2 instances in three regions and use Amazon Elastic Load Balancer.

Answer: C

Explanation:

Reference: https://media.amazonwebservices.com/pdf/AWS_Security_Whitepaper.pdf (page 8)