Among the following acids whose basicity is two

Basicity of an acid is the number of replaceable ‘ H + ions’ in one molecule of the acid by the cation. For ${\mathrm{H}}_2{\mathrm{SO}}_4$,basicity is 2. Since there is 2 replaceable ‘H atoms’ present.

For ${\mathrm{H}}_3{\mathrm{PO}}_3,$basicity is 2. Because there is 2 replaceable ‘H atoms’ present.