Two blocks of masses m and 2m are placed one over the other as shown in figure. The coefficient of friction between m and 2m is $\mathrm{\mu }$ and between 2m and ground is $\frac{\mu }{3}$. If a horizontal force F is applied on upper block and T is tension developed in string, then choose the incorrect alternative.

• A

  $\text{ If }F=\frac{\mu }{3}mg,T=0$

• B

  $\text{ If }F=\mu mg,T=0$

• C

  $\text{ If }F=2\mu mg,T=\frac{\mu mg}{3}$

• D

  $\text{ If }F=3\mu \mathrm{mg},T=0$