Final answer:
The correct balanced equation for the sodium borohydride reduction reaction where all elements are balanced is NaBH4 + 2H2O → NaBO2 + 3H2, which is option (b).
Step-by-step explanation:
The balanced equation for the sodium borohydride reduction is the one where the number of atoms for each element on the reactant side is equal to the number on the product side. Sodium, hydrogen, boron, and oxygen should all be balanced. Only option (b) meets this criterion :
NaBH4 + 2H2O → NaBO2 + 3H2
This equation conserves the number of sodium, hydrogen, boron, and oxygen atoms on both sides. In options a, c, and d, hydrogen is not balanced as there would be more hydrogen atoms on the reactant side than on the product side. Therefore, the correct option is b. In any chemical equation, it is crucial to ensure the conservation of mass by having an equal number of each type of atom on both sides of the equation.