Gills are an internal adaptation in fish that allow them to take out from the water as it passes over the gills and releases into the water. A. Carbon dioxide, oxygen
B. Nutrients, Waste
C. Salt, Pure Water
D. Oxygen, Carbon Dioxide

A. Oxygen and carbon dioxide

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).