You have a website which is using a custom theme made specifically for that website.

Drupal core provides a specific setting for whether node add/edit forms should use the administration theme. On the Appearance page, this is the checkbox labeled “Use the administration theme when editing or creating content” . When that setting is enabled, content creation and editing routes are treated as admin-theme routes; when it is disabled, those forms use the site’s default front-end theme instead, while the rest of the administration area can still use the admin theme such as Claro. This behavior is implemented in core through the node.settings configuration value use_admin_theme and the node route subscriber that marks node operation routes as admin routes only when that setting is turned on.

That makes option A correct. Option B would not solve the requirement, because setting the admin theme as the default theme would affect the whole site’s front-end presentation. Options C and D are incorrect because Drupal does not use a role permission like “View Admin Theme” to control this behavior for node edit pages. The documented control for this requirement is the Appearance-page checkbox tied to node.settings.use_admin_theme .