The dimensional formula of axb in the relation $\mathrm{P}=\frac{\mathrm{b}-{\mathrm{x}}^2}{\mathrm{at}}$  is, where P is power, x is  distance and t is time      

• A

  $\left[{\mathrm{M}}^{-1}{\mathrm{L}}^2{\mathrm{T}}^2\right]$

• B

  $\left[\mathrm{M}{\mathrm{L}}^2{\mathrm{T}}^2\right]$

• C

  $\left[{\mathrm{ML}}^2{\mathrm{T}}^{-2}\right]$

• D

  $\left[{\mathrm{M}}^{-1}{\mathrm{LT}}^2\right]$