Under the same reaction conditions,initial concentration of $1.386 \ mol \ dm^{-3}$ of a substance becomes half in $40 \ s$ and $20 \ s$ through first-order and zero-order kinetics respectively. Ratio $\left(\frac{k_{1}}{k_{0}}\right)$ of the rate constants for first-order $\left(k_{1}\right)$ and zero-order $\left(k_{0}\right)$ of the reactions is

• A
  $0.5 \ mol^{-1} \ dm^{3}$
• B
  $0.5 \ mol \ dm^{-3}$
• C
  $1.0 \ mol \ dm^{-3}$
• D
  $2.0 \ mol^{-1} \ dm^{3}$