Users typically forget to add components when they create new issues. As a result, most of the newly created issues get assigned to Tom, who is the project lead.
Tom reviews all of the issues, and wants to triage them based on component selection. But when he edits an issue and adds a component, the assignee does not change.
Why does the assignee not change when adding a component to an issue?
Auto-assignment with components only works when creating issues. When a new issue is created, the system can automatically assign it to the relevant person based on the selected component. However, if the component is added or updated after the issue has been created, the auto-assignment feature does not trigger a reassignment. Therefore, Tom has to manually change the assignee if the component is added or modified post-creation.
A is the correct answer
A is correct this process seems to only work during creation of a new issue. https://confluence.atlassian.com/adminjiraserver/managing-components-938847187.html#Managingcomponents-default_assignee
Jira Automation might be an option post creation, but it doesn't state that in Q. Selecting a default assignee When you set a default assignee for a component, this component assignee will override the project's default assignee for new issues with this component. So, when creating issues with this component, you’ll be able to leave the option Automatic in the Assignee field and won’t need to select an assignee from the list of users. Jira will determine the component assignee and set this user in the new issue.