Solution:
Concept- The difference between monobasic, dibasic, and tribasic acids is that a monobasic acid only contains one replaceable hydrogen atom, whereas a dibasic acid has two, and a tribasic acid has three.structure of H3PO2 contains only one P-OH bond; since number of P-OH bonds determine the basicity of oxo acids of phosphorus. H3PO2 which has single P - OH bond is monobasic.H3PO2 and H4P2O7 is monobasic and tribasic acids respectively. Monobasic acid has one hydrogen atom to replace and tetrabasic acid has four hydrogen atoms to replace.
Hence, the correct answer is option (3).
