The correct answer is B) Steam cleaning and water washing are both capable of generating electrostatic charges within a tank. This is correct because during tank cleaning operations, the agitation of the liquid and vapor can generate static electricity. Both steam cleaning and water washing can create these electrostatic charges, which can potentially ignite any flammable vapors present in the tank. This is an important safety consideration when cleaning cargo tanks that have contained flammable substances like crude oil. The other answer choices are incorrect because: A) The flame point is not the main hazard, it's the potential for static discharge ignition. C) Recirculating the washing water does not eliminate the static charge hazard. D) Disconnecting the hoses is not the key safety factor, it's the potential for static buildup during the cleaning process.