The first step Niven has to do in his calculation is to Balanced the chemical equation. The answer is letter A. The key in the balancing of chemical reaction is to make sure that you got the exact chemical formula of the substance that is reacting and the yielded product. After getting the formula, identify first the hardest element/atom to be balanced such as Na, Zn, Cl, etc. Then proceed to the easier ones such as O, H. Make sure to not the atoms present in the molecule of the substance.