The densities of ice and water are $\rho$ and $\sigma$ respectively. What is the change in volume when a mass $M$ of ice melts?

• A
  $\frac{M}{\sigma - \rho}$
• B
  $\frac{\sigma - \rho}{M}$
• C
  $M \left[ \frac{1}{\rho} - \frac{1}{\sigma} \right]$
• D
  $\frac{1}{M} \left[ \frac{1}{\rho} - \frac{1}{\sigma} \right]$