A block of mass m is in contact with the cart C as shown in the Figure. The coefficient of static friction between the block and the cart is $\mathrm{\mu }$. The acceleration s of the cart that will prevent the block from falling satisfies :

• A

  $\mathrm{\alpha }<\frac{\mathrm{g}}{\mathrm{u}}$

• B

  $\mathrm{\alpha }>\frac{\mathrm{mg}}{\mathrm{\mu }}$

• C

  $\mathrm{\alpha }>\frac{\mathrm{g}}{\mathrm{\mu m}}$

• D

  $\mathrm{\alpha }\ge \frac{\mathrm{g}}{\mathrm{\mu }}$