What kind of fossil is a shark tooth?

Fossil teeth comprise much of the fossil record of the Elasmobranchii, extending back to hundreds of millions of years. A shark tooth contains resistant calcium phosphate materials. The most ancient types of sharks date back to 450 million years ago, during the Late Ordovician period, and are mostly known by their fossilized teeth.

i think that d. wind is the answer.   i missed the question when i answered a. currents.