Your team is responsible for an AWS Elastic Beanstalk application. The business requires that you move to a continuous deployment model, releasing updates to the application multiple times per day with zero downtime. What should you do to enable this and still be able to roll back almost immediately in an emergency to the previous version?

Answer options:

A.Enable rolling updates in the Elastic Beanstalk environment, setting an appropriate pause time for application startup.
B.Create a second Elastic Beanstalk environment running the new application version, and swap the environment CNAMEs.
C.Develop the application to poll for a new application version in your code repository; download and install to each running Elastic Beanstalk instance.
D.Create a second Elastic Beanstalk environment with the new application version, and configure the old environment to redirect clients, using the HTTP 301 response code, to the new environment

Answer – B
The AWS Documentation mentions the below
Because Elastic Beanstalk performs an in-place update when you update your application versions, your application may become unavailable to users for a short period of time. It is possible to avoid this downtime by performing a blue/green deployment, where you deploy the new version to a separate environment, and then swap CNAMEs of the two environments to redirect traffic to the new version instantly
For more information on Elastic beanstalk swap URL please see the below link:
http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features.CNAMESwap.html