The resources for a business-critical, three-tier web application are expressed in a series of AWS CloudFormation templates. The application is using Amazon RDS for data and Amazon ElastiCache for session state. Users have reported degraded performance in the application. A DevOps Engineer notices that the T2 instance type is being used for the application tier and CPU usage is at 100% in Amazon CloudWatch.
What process should the Engineer follow to restore operations with the LEAST amount of disruption to the end users?

A. Write a new CloudFormation template to include Amazon CloudFront in the environment, launch the stack, and update the Amazon Route 53 A record
B. Launch a new CloudFormation stack for the application tier using the M4 instance type, run acceptance tests against the new stack, and update the Amazon Route 53 A record
C. Update the CloudFormation stack for the application tier using the T2 Unlimited option, run acceptance tests against the new stack, and update the Amazon Route 53 A record
D. Launch a new CloudFormation stack for all tiers of the application in a different region, run acceptance tests against the new stack, and update the Amazon Route 53 A record