The correct answer is A) Minimize oil consumption by separating oily vapors being vented to the atmosphere. The purpose of the air/oil separator in a gas turbine lube oil system is to minimize oil consumption by separating oily vapors from the air being vented to the atmosphere. This helps prevent the loss of lubricating oil, which would otherwise be discharged into the environment. The air/oil separator achieves this by mechanically removing the oil mist from the vent air, allowing the oil to be returned to the system while the cleaned air is safely vented. The other options are incorrect because they do not fully capture the primary purpose of the air/oil separator, which is to conserve lubricating oil and prevent environmental pollution.