Answer:
Options A and C are correct
Single atoms should be done last.
Balancing chemical equations involves trial and error.
Explanations:
Chemical equations are known to be balanced if the total number of elements on the reactant side is equal to the total elements on the product side.
Balancing of chemical equations may not be determined at once, hence the use of trial and method is crucial.
Also, atoms that are in only one of the reactants and only one of the products should be done first while single atoms should be done last.