(d) : Higher is the oxidation state of the central atom, greater is the acidity.
Hence, HClO4 is a stronger acid than HClO3. HNO3 is a stronger acid than HNO2.
Now, greater is the electronegativity and higher is the oxidation state of the central atom, greater is the acidity. Hence H2SO3 is a stronger acid than H3PO3.
Due to higher dissociation energy of H – F bond and molecular association due to hydrogen bonding in HF, HF is a weaker acid than HCl.