Final answer:
The appropriate treatment for a jellyfish sting is to irrigate the wound with vinegar and immerse the affected leg in hot water to alleviate pain and neutralize toxins.
Step-by-step explanation:
The treatment for a jellyfish sting includes specific steps that are critical in order to alleviate pain and prevent further injury. The correct treatment is A) irrigating the wound with vinegar and immersing his leg in hot water. Vinegar helps to neutralize the stinging cells, called nematocysts, and hot water immersion (typically at 104-113°F or 40-45°C) helps to reduce pain and inactivate the toxins. Options B, C, and D are incorrect because they could potentially cause the nematocysts to discharge more venom or lead to further injury.