<prompt> The retention in the cast metal restoration is mainly by:Diverging vertical wallsParallel vertical wallsLuting cementAll of the above  <response>: Cast-metal intracoronal restorations, referred to as inlay restorations, rely on diverging vertical walls that are almost parallel and a luting cement to provide retention of the casting in the tooth.Sturdevant operative dentistry 7th Edition, Page No:120 