What is flameover (rollover)?

A) A rapidly occurring transitional event in the development of a compartment fire
B) The condition whereby unburned fuel (pyrolyzate) from the originating fire has accumulated in the ceiling layer to a sufficient concentration that it ignites and burns
C) The ignition of unburned pyrolyzates due to sudden influx of air which ignites and results in an extremely rapid burning of gases/pyrolysis products being forced out through an opening
D) The sudden ignition of a diffused fuel suspended in the atmosphere

B