The rate of decay of mass of a certain substance at time $t$ is proportional to the mass at that instant. The time during which the original mass of $m_{0} \text{ gm}$ will be reduced to $m_{1} \text{ gm}$ is (where $K$ is the constant of proportionality).

• A
  $K \log \left(\frac{m_{1}}{m_{0}}\right)$
• B
  $\left(\frac{1}{K}\right) \log \left(\frac{m_{1}}{m_{0}}\right)$
• C
  $\left(\frac{1}{K}\right) \log \left(\frac{m_{0}}{m_{1}}\right)$
• D
  $K \log \left(\frac{m_{0}}{m_{1}}\right)$