Answer - B
The AWS Documentation mentions the following.
AWS CloudFormation StackSets extends the functionality of stacks by enabling you to create, update, or delete stacks across multiple accounts and regions with a single operation. Using an administrator account, you define and manage an AWS CloudFormation template and use the template as the basis for provisioning stacks into selected target accounts across specified regions.
Option A is incorrect since this is used to make changes to the running resources in a stack.
Option C is incorrect since these are stacks created as part of other stacks.
Option D is incorrect since this is used in conjunction with Code Pipeline.
For more information on Stack Sets, please refer to the below URL-
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/what-is-cfnstacksets.html