Which one are only the elements? a. Nitrogen gas (N2), Carbon dioxide (CO2), Sulfur dioxide (SO2)

b. Steel, milk, Chlorine gas (Cl2)

c. Aluminium (Al), iron (Fe), Sulfur (S)

d. Steam (H2O), Sulfuric acid (H2SO4), Iodine gas (I2)

i think it's C

Explanation:

in theory, limestone is composed principally of the compound calcium carbonate - caco3, but in reality this compound is deposited in conditions involving a number of other compounds as impurities so it ends up being a mixture of many compounds.

hope this : -)

tony (lordcaos066)