A ball of mass $2 \mathrm{~kg}$ collides with another ball of mass $\mathrm{M}$ at rest. If the collision is elastic and after the collision, the first ball moves with $\frac{1}{3}$ of its initial velocity in the same direction. then the mass of second ball is

• A

  $2.5 \mathrm{~kg}$
• B

  $3.5 \mathrm{~kg}$
• C

  $3.0 \mathrm{~kg}$
• Correct answer
  D

  $1.0 \mathrm{~kg}$

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