Chemistry - Complete P-block Question with Solution | TestHub

Basicity depends on the number of ionizable −OH hydrogens, not total H atoms.

H₃PO₃ has 2 ionizable H, while H₃PO₂ has 1; therefore H₃PO₃ > H₃PO₂ → (D) correct.

For (C), the basicity values increase as: $1<2<4$, so the given order is correct.

In (A) and (B), the compounds do not follow the required increase in ionizable −OH groups.

Hence, correct options are C, D.