The balanced equation for the complete combustion of hydrogen is:

The balanced equation for the complete combustion of hydrogen involves understanding the stoichiometry of the reaction. During the complete combustion of hydrogen, hydrogen gas (H2) reacts with oxygen gas (O2) to produce water (H2O) and release energy in the form of heat.

The correct equation is:

2H2 + O2 = 2H2O + heat

In this balanced equation, two molecules of hydrogen gas react with one molecule of oxygen gas to form two molecules of water. This aligns with the law of conservation of mass, which states that matter cannot be created or destroyed in a closed system. Therefore, it is crucial to ensure that the number of atoms of each element on the reactant side (left) matches the number on the product side (right).

In option C, there are two hydrogen molecules contributing a total of four hydrogen atoms, and one oxygen molecule providing two oxygen atoms, thus yielding two water molecules, which contain the same total number of atoms: two oxygen and four hydrogen.

This equation effectively illustrates the complete combustion of hydrogen and correctly represents the stoichiometric balance required in chemical reactions. Other options either do not balance correctly or represent incorrect ratios of reactants to products.