Final answer:
The appropriate extinguishers for an oil-based fire caused by railway derailment are CO2 or dry chemical extinguishers, as they can effectively smother the fire without causing the spread of flaming oil.
Step-by-step explanation:
If there is the opportunity to do so safely, the appropriate type of extinguisher to use for an oil-based fire, such as one caused by sparks from a derailment, is a CO2 (carbon dioxide) or dry chemical extinguisher. Both types of extinguishers work well to fight flammable liquid fires (Class B) by displacing oxygen (CO2 extinguishers) or by interrupting the chemical reaction at the fire's surface (dry chemical extinguishers).
Fire extinguishers containing water should not be used on oil-based fires because oil is less dense than water and will float, potentially spreading the fire. Powder extinguishers could be considered if they are dry chemical powders designed for Class B fires. Halon extinguishers are effective as well but are less commonly used due to environmental concerns.