$A$ thermally insulated vessel contains an ideal gas of molecular mass $M$ and ratio of specific heats $\gamma$. It is moving with speed $v$ and is suddenly brought to rest. Assuming no heat is lost to the surroundings,its temperature increases by

• A
  $\frac{(\gamma - 1)}{2(\gamma + 1)R}Mv^2$
• B
  $\frac{(\gamma - 1)}{2\gamma R}Mv^2$
• C
  $\frac{\gamma Mv^2}{2R}$
• D
  $\frac{(\gamma - 1)}{2R}Mv^2$