You are cleaning the tanks after carrying a cargo of crude oil. Which statement is TRUE? （）

A. Washing water should be recirculated if possible because it has the same electric potential as the cargo tank being cleaned
B. The hoses to portable cleaning machines should be disconnected before the machines are removed from the tank
C. The principal hazard with steaming cargo tanks is raising the ambient temperature above the flame point of the cargo residue
D. Steam cleaning and water washing are both capable of generating electrostatic charges within a tank