Which digit should come in the box so that following subtraction is correct? \[-\underline{\begin{align} & \underline{\begin{matrix} 6 & 4 \\ 2 & \\ \end{matrix}} \\ & 3\,\,\,\,\,\,\,\,5 \\ \end{align}}\]

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