20. You want to enter a gas-free cargo tank on oil tanker and atmospheric condition of cargo tankwas checked prior to entering. What hydrocarbon vapor concentration you should get to ensuresafety?
(A) Less than 35% LFL (Lower Flammable Limit).
(B) Less than 10% LFL (Lower Flammable Limit).
(C) Less than 5% LFL (Lower Flammable Limit).
(D) Less than 1% LFL (Lower Flammable Limit).