28. A non-inert cargo tank washing was carried out under both thesource of ignition and flammability of the tank atmosphere arecontrol. In what level of hydrocarbon vapor concentration you muststop the tank washing operation?
(A) More than 50% LFL (Lower Flammable Limit).
(B) More than 35% LFL (Lower Flammable Limit).
(C) More than 10% LFL (Lower Flammable Limit).
(D) More than 1% LFL (Lower Flammable Limit).