In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{P8Q}\,\,\,\text{:}\,\,\,\,\text{Q7P}\] \[\text{M4N}\,\,\,\text{:}\,\,\,\,\text{N3M}\] \[\text{A2B}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  X8Y       
• B.         Y1X   
• C.  B1A      
• D.         A1B