In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{8}\,\,\,\text{:}\,\,\,\,\text{11}\] \[\text{15}\,\,\,\text{:}\,\,\,\,\text{18}\] \[\text{3}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  7            
• B.         8        
• C.  6            
• D.         9