Three samples of the same gas $A, B$ and $C$ $(\gamma = 3/2)$ initially have equal volume. Now the volume of each sample is doubled. The process is adiabatic for $A$,isobaric for $B$ and isothermal for $C$. If the final pressures are equal for all three samples,the ratio of their initial pressures is:

• A
  $2\sqrt{2} : 2 : 1$
• B
  $2\sqrt{2} : 1 : 2$
• C
  $\sqrt{2} : 1 : 2$
• D
  $2 : 1 : \sqrt{2}$