Answer:
D - Balance the equation
Step-by-step explanation:
A balanced chemical equation shows the number of moles, volume, or mass of a compound/molecule that combines with another in order to give some certain products.
To quantitatively follow how reactants combine to form some desired products, one must express the equation in a balanced form so as to be able to carefully measure the amount of matter and the moles involved in a specific reaction. In chemistry, such calculation falls under stoichiometry (stoicheon means atom and metron is measurement).