Explanation
The below diagram shows how this can be done

1) First create a new ELB which will be used to point to the new production changes.
2) Use the Weighted Route policy for Route53 to distribute the traffic to the 2 ELB's based on a 80-20% traffic scenario. This is the normal case, the % can be changed based on the requirement.
3) Finally when all changes have been tested, Route53 can be set to 100% for the new ELB.
Option A is incorrect because this is a failover scenario and cannot be used for Blue green deployments. In Blue Green deployments, you need to have 2 environments running side by side.
Option B is incorrect, because you need to a have a production stack with the changes which will run side by side.
Option D is incorrect because this is not a blue green deployment scenario. You cannot control which users will go the new EC2 instances.
For more information on blue green deployments, please refer to the below document link: from AWS
* https://dOawsstatic.com/whitepapers/AWS_Blue_Green_Deployments.pdf

... disposable upgrades offer a simpler way to know if your application has unknown dependencies. The
underlying EC2 instance usage is considered temporary or ephemeral in nature for the period of
deployment until the current release is active. During the new release, a new set of EC2 instances are
rolled out by terminating older instances. This type of upgrade technique is more common in an
immutable infrastructure.
Reference: https://d0.awsstatic.com/whitepapers/overview-of-deployment-options-on-aws.pdf

https://docs.aws.amazon.com/codepipeline/latest/userguide/integrations-action-type.html#integrations-test https://docs.aws.amazon.com/codepipeline/latest/userguide/integrations-action-type.html#integrations-deploy

Ansible Playbooks are a series of plays and must contain at a minimum, one play. A play generally consists of hosts to run on, a list of tasks, variables and roles, and any additional instructions, such as connection type, fact gathering, remote username, etc. that the tasks will need to complete. The only requirement for a valid play is to declare the hosts. Reference:
http://docs.ansible.com/ansible/playbooks_intro.html