Consider a block and trolley system as shown in figure. If the coefficient of kinetic friction between the trolley and the surface is $0.04$, the acceleration of the system in $\mathrm{m} {\mathrm{s}}^{-2}$ is: (Consider that the string is massless and unstretchable and the pulley is also massless and frictionless) :

• A

  $3$
• B

  $4$
• Correct answer
  C

  $2$
• D

  $1.2$

Hence, the correct answer is option: 'C'.