A $2$ meter long scale with least count of $0.2 \mathrm{cm}$ is used to measure the locations of objects on an optical bench. While measuring the focal length of a convex lens, the object pin and the convex lens are placed at $80 \mathrm{cm}$ mark and $1 \mathrm{m}$ mark, respectively. The image of the object pin on the other side of lens coincides with image pin that is kept at $180 \mathrm{cm}$ mark. The $\%$ error in the estimation of focal length is:

• A

  $0.85$
• Correct answer
  B

  $1.70$
• C

  $1.02$
• D

  $0.51$

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