The correct option is Children.

The Children branch iterates over the issues that are directly contained within an Epic so the automation can add a comment to each story or task inside that Epic. Using this branch runs the comment action once per child issue which meets the requirement to touch every issue in the Epic.

Linked Issues is incorrect because it targets issues connected by issue links such as relates to or blocks and not specifically the child issues of an Epic.

Parent is incorrect because that branch moves from a child issue to its parent and does not iterate through the issues inside an Epic.

Epic (Parent) is incorrect because it is used when you start from a child and want to operate on its Epic rather than when you need to act on all issues within an Epic.

Sub-tasks is incorrect because it targets sub-tasks of an individual issue and will not reach the standard stories or tasks that are children of an Epic.

Full AWS Practitioner Certification Question