The measured value of the length of a simple pendulum is $20 \mathrm{cm}$ with $2 \mathrm{mm}$ accuracy. The time for $50$ oscillations was measured to be $40$ seconds with $1$ second resolution. From these measurements, the accuracy in the measurement of acceleration due to gravity is $N\%$. The value of $N$ is:

• A

  $4$
• B

  $8$
• Correct answer
  C

  $6$
• D

  $5$

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