In these questions, the letters are linked in some way. Identify the relation and complete the last box. \[\text{10A}\,\,\,\text{:}\,\,\,\,\text{20B}\] \[\text{30C}\,\,\,\text{:}\,\,\,\,\text{40D}\] \[\text{50E}\,\,\,\text{:}\,\,\,\,\text{?}\]

• A.  60F       
• B.         60H     
• C.  50F       
• D.         50H