In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{101}\,\,\,\text{:}\,\,\,\,\text{111}\] \[\text{111}\,\,\,\text{:}\,\,\,\,\text{121}\] \[\text{505}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  555                       
• B.         525       
• C.  515                       
• D.         252