Final answer:
The best descriptor for a shark tooth fossil is 'preserved' because it involves the actual material of the organism's body being retained over time, which aligns with the characteristics of shark teeth that are made of hard materials capable of withstanding long periods without major alteration.
Step-by-step explanation:
The fossil of a shark tooth typically falls under the category of a body fossil, which is a category of fossils where the actual parts of the organism are preserved. Given the choices provided and the nature of the shark tooth as part of the physical body, it would not be considered a mold, cast, or trace. A mold is an impression of the organism, a cast is formed when a mold is filled with sediment, and trace fossils are evidence of the organism's activity, like footprints or burrows.
When considering the term petrified, this usually refers to a process where an organism's organic material is replaced by minerals over time, turning it into stone. However, in the context of a shark tooth, preserved likely describes the fossil better. Sharks' teeth are made of hard material that can survive for a long time and become fossils without needing to go through the petrification process.
Therefore, when looking specifically at a shark tooth, which is part of the species sharks, the description that best fits the fossil is likely preserved (d) because it involves the original material of the organism's body remaining, rather than being replaced by another mineral substance as with petrification.