You are in charge of designing a number of Cloudformation templates for your organization. You are required to make changes to the stack resources every now and then based on the requirement. How can you check the impact of the change to resources in a cloudformation stack before deploying changes to the stack?

Answer options:

A.There is no way to control this. You need to check for the impact beforehand.
B.Use Cloudformation change sets to check for the impact to the changes.
C.Use Cloudformation Stack Policies to check for the impact to the changes.
D.Use Cloudformation Rolling Updates to check for the impact to the changes.

Answer – B
The AWS Documentation mentions
When you need to update a stack, understanding how your changes will affect running resources before you implement them can help you update stacks with confidence. Change sets allow you to preview how proposed changes to a stack might impact your running resources, for example, whether your changes will delete or replace any critical resources, AWS CloudFormation makes the changes to your stack only when you decide to execute the change set, allowing you to decide whether to proceed with your proposed changes or explore other changes by creating another change set. You can create and manage change sets using the AWS CloudFormation console, AWS CLI, or AWS CloudFormation API.
For more information on Cloudformation change sets, please visit the below url
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-changesets.html