In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{CD}\,\,\,\text{:}\,\,\,\,\text{GH}\] \[\text{EF}\,\,\,\text{:}\,\,\,\,\text{IJ}\] \[\text{KL}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  OP        
• B.         MN     
• C.  QR        
• D.         RS