Final answer:
The best revision that clarifies the idea of finding a sand dollar as a special event is 'Finding a perfect sand dollar is like finding buried treasure,' as it underscores the thrill and rarity of such a discovery.
Step-by-step explanation:
The question asks which revision of the underlined sentence best clarifies the idea that finding a sand dollar is a special event. Considering the context that describes the joy and luck associated with finding a fully intact sand dollar, the best revision that clarifies this idea is:
D. Finding a perfect sand dollar is like finding buried treasure.
This comparison captures the excitement and rarity of the discovery, paralleling the thrill and value often associated with treasure hunting. It emphasizes that the experience is not only about the physical object but also the rarity and the joy of the discovery process.