ANSWER
Atom
option A
EXPLANATION
The quantities of reactants and products can be determined using a stoichiometry ratio.
Stoichiometry is defined as the calculation of the quatities of reactants and products in a chemical reaction using the relationship established in a balancing chemical equation.
To balance a chemical reaction, apply the law of conservation of mass
Law of conservation mass states that matter can neither be destroyed nor created but can be transformed from one form to another.
Therefore, the units of measurements that would be used to determine the quantities of reactants and products is atom
The correct answer is option A
