Two blocks of masses $10 \mathrm{kg}$ and $30 \mathrm{kg}$ are placed on the same straight line with coordinates $\left(0,0\right)\mathrm{cm}$ and $\left(x,0\right)\mathrm{cm}$ respectively. The block of $10 \mathrm{kg}$ is moved on the same line through a distance of $6 \mathrm{cm}$ towards the other block. The distance through which the block of $30 \mathrm{kg}$ must be moved to keep the position of centre of mass of the system unchanged is

• A

  $4 \mathrm{cm}$ towards the $10 \mathrm{kg}$ block
• B

  $2 \mathrm{cm}$ away from the $10 \mathrm{kg}$ block
• Correct answer
  C

  $2 \mathrm{cm}$ towards the $10 \mathrm{kg}$ block
• D

  $4 \mathrm{cm}$ away from the $10 \mathrm{kg}$ block

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