AIIMS 2019 Chemistry Oxo-acids of Phosphorus MCQ Question

Hypophosphorus acid (H₃PO₂) has a structure that includes one phosphorus atom bonded to two hydroxyl groups (–OH) and one double-bonded oxygen (P=O), resulting in a total of two acidic protons and one non-bonded oxygen. In contrast, orthophosphoric acid (H₃PO₄) has three acidic protons and no non-bonded oxygens, phosphorus acid (H₃PO₃) has two acidic protons and one non-bonded oxygen, and pyrophosphoric acid (H₄P₂O₇) has four acidic protons but no non-bonded oxygens, making option B the only one that accurately describes the structure with respect to its acidic protons and non-bonded oxygens.