Answer: (C) Black $\gt$ Red $\gt$ White $\quad$
White phosphorus is the least stable, the most reactive, the most volatile, while Black phosphorus is the least reactive allotrope and the thermodynamically stable form below $550^{\circ}$.
Red phosphorus is highly reactive and ignites at about $300^{\circ}$ though it is still more stable than white phosphorus, which ignites at about $30^{\circ}$.
