$\quad$ A ball whose density is $0.4 \times 10^{3} \mathrm{~kg} / \mathrm{m}^{3}$ falls into water from a height of $9 \mathrm{~cm}$. To what depth does the ball sink?

• A

  $2 \mathrm{~cm}$
• Correct answer
  B

  $6 \mathrm{~cm}$
• C

  $4.5 \mathrm{~cm}$
• D

  $2.25 \mathrm{~cm}$

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