Final answer:
Calcite is the word that best fits the definition of calcium carbonate, when calcium, oxygen, and carbon combine.
Step-by-step explanation:
The word from the list that best fits the definition is calcite.
Calcite is formed when calcium, oxygen, and carbon combine. Calcium carbonate, which is the chemical name for calcite, has the formula CaCO3.
In nature, calcite is found in limestone and is also a structural material in many organisms, including the teeth of sea urchins.
Calcite , oxygen, and carbon combine to form calcite