The correct answer is D) Gas pressures should be maintained at the highest permissible level throughout the discharging process. This is correct because maintaining the highest permissible level of inert gas pressure in the cargo tank helps prevent the formation of a flammable atmosphere during discharge. High gas pressures prevent air from entering the tank, which could lead to the creation of a potentially explosive gas mixture. Keeping the pressure high ensures that the tank remains inerted and safe throughout the discharge operation. The other options are incorrect. A) and C) describe potential problems caused by high gas pressures, which is the opposite of the correct practice. B) refers to pyrophoric oxidation, which is not directly related to the purpose of maintaining high inert gas pressures during discharge.