In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{555}\,\,\,\text{:}\,\,\,\,\text{555}\] \[\text{123}\,\,\,\text{:}\,\,\,\,\text{321}\] \[\text{424}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  444                       
• B.         222       
• C.  242                       
• D.         424