If the fuel does not have enough oxygen to burn completely co2 and h2o, there can be two additional products. what are they?

Assuming you're referring to a combustion reaction, the products can also be N2, CO, and NOx, x being the subscript or number of oxygens in the nitrogen-oxygen compound.

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).

i think that the answer is c