The soldiers of Napolean army while at Alps during freezing winter suffered a serious problem as regards to the tin buttons of their uniforms. White metallic tin buttons got converted to grey powder. This transformation is related to

• A

  an interaction with nitrogen of the air at very low temperatures
• B

  an interaction with water vapour contained in the humid air
• C

  a change in the partial pressure of oxygen in the air
• Correct answer
  D

  a change in the crystalline structure of tin

Hence, the correct answer is option: 'D'.