The system is pushed by a force F as shown in the figure. All surfaces are smooth except between B and C. Coefficient of friction between B and C is $\mathrm{\mu }$ . Minimum value of F to prevent block B from downward slipping is

• A

  $\left(\frac{3}{2\mathrm{\mu }}\right)\mathrm{mg}$

• B

  $\left(\frac{5}{2\mathrm{\mu }}\right)\mathrm{mg}$

• C

  $\left(\frac{5}{2}\right)\mathrm{\mu mg}$

• D

  $\left(\frac{3}{2}\right)\mathrm{\mu mg}$