50. Which of the following statements is incorrect? (A) Flashover is the transition phase in which all combustible materials in an enclosed area ignite nearly simultaneously due to rapid heat buildup. (B) Backdraft occurs when accumulated hot gases in an oxygen-deprived space ignite explosively after fresh air is introduced. (C)Thermal layering is the stratification of heat and smoke into layers, with hotter gases accumulating near the ceiling. (D) Fire load is the total number of firefighters assigned to an emergency incident.