Express \[\left[ \frac{-1}{4}-\left( \frac{-1}{6} \right) \right]\div \left[ \frac{1}{3}+\left( \frac{1}{2} \right) \right]\] in the simplest form.

• A. \[\frac{-2}{3}\]                                 
• B. \[\frac{1}{2}\]  
• C. \[\frac{2}{3}\]                   
• D.        \[\frac{-1}{2}\]