You are customizing search results in a SharePoint Server 2013 server farm. You need to create a webpage that users can use to search Knowledge Base articles stored in an external Microsoft SQL Server

The Search results page layout is the correct page type for rendering and displaying search result sets to users visiting the new page. A content type hub, part of the Managed Metadata Service Application, publishes external content types defined through Business Connectivity Services (BCS) for the SQL Server database across all site collections, making the Knowledge Base content type uniquely resolvable by search and effectively scoping results to that external source.

The Search box page layout renders only a search input field and cannot display result sets, so users would have no way to see Knowledge Base articles returned from their query.

The Search box page layout is the wrong choice for a results page, and while a result source with query transformation does scope results, it does not address the need to expose external SQL Server content types across the farm via BCS.

A result source with query transformation is a valid scoping mechanism but paired with the Search box page layout, which cannot render results, making this combination non-functional for the stated requirement.