A block of mass m, lying on a horizontal plane, is acted upon by a horizontal force P and another force Q, inclined at an angle $\mathrm{\theta }$ to the vertical. The block  ill remain in equilibrium, if the coefficient of friction between it and the surface is:

• A

  $\frac{(\mathrm{P}+\mathrm{Q} \sin \mathrm{\theta })}{(\mathrm{mg}+\mathrm{Q} \cos \mathrm{\theta })}$

• B

  $\frac{(\mathrm{P} \cos \mathrm{\theta } +\mathrm{Q})}{(\mathrm{mg}-\mathrm{Q} \sin \mathrm{\theta })}$

• C

  $\frac{(\mathrm{P} + \mathrm{Q} \cos \mathrm{\theta })}{(\mathrm{mg} +\mathrm{Q} \sin \mathrm{\theta })}$

• D

  $(\mathrm{P} \sin \mathrm{\theta }-\mathrm{Q})-(\mathrm{mg}-\mathrm{Q} \cos \mathrm{\theta })$