Why a dry cell becomes dead after a long time even it has not been used?

Hint: A dry cell has the electrolyte immobilized as a glue, with just enough dampness in it to permit current to stream.

Explanation for correct option:

• A dry cell has an electrolyte and a couple of cathodes.
• A dry cell consistently has some inside obstruction.
• Due to this inner obstruction, there is in every case some voltage drop related with the cell regardless of whether the cell isn't being used, and ultimately become dead after quite a while.
• And ammonium chloride $\left(N{H}_{4}Cl\right)$ is acidic in nature. A zinc holder is consumed.

Hence, option (C) is correct.