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

Tin exists in different elemental forms (allotropes) depending on the temperature:

• White Tin ($$\beta$$-tin): This is the familiar, shiny, metallic form of tin that has a tetragonal crystalline structure. It is stable at room temperature and higher temperatures.
• Grey Tin ($$\alpha$$-tin): This is a non-metallic, brittle, powdery form of tin that has a diamond cubic crystalline structure.

The Temperature Factor

The transition point between these two structures is $$13.2^\circ\text{C}$$ ($$55.8^\circ\text{F}$$).

When the temperature drops well below $$13.2^\circ\text{C}$$—such as during a freezing alpine winter—the white metallic tin naturally wants to change into grey tin. Because grey tin has a much lower density, the atomic structure expands, causing the solid metal buttons to swell, become incredibly brittle, and eventually crumble into a grey powder.

Hence, Option D is Correct