Final answer:
The correct answer is option b. The word 'douse' in the sentence refers to the action of trying to extinguish the fire with water, despite the efforts being unsuccessful.
Step-by-step explanation:
The word douse as it is used in the sentence means to extinguish the fire with water. Despite efforts to douse the fire, the landfill continued to burn, indicating that the attempts to put out the fire were unsuccessful.
In this context, douse is the opposite of ignite, which means to cause something to start burning; it is different from fuel, which means to support or encourage the fire; and isolate, which means to separate something from other things. Therefore, the correct option in the final answer is b) Extinguish.