Consider the statements: (I) H3PO3 is dibasic whereas H3PO2 is monobasic. (II) XeF4 is square planar. (III) H3PO2 acts as a reducing agent. (IV) N2O4…

(I) true: $\mathrm{H_3PO_3}$ has two P-OH groups and one P-H, $\mathrm{H_3PO_2}$ has one P-OH. (II) true: Xe has $4$ bond pairs and $2$ lone pairs in an octahedral arrangement, giving square planar shape. (III) true: the P-H bonds make hypophosphorous acid a strong reductant (it reduces $\mathrm{Ag^+}$ to Ag). (IV) false: $\mathrm{N_2O_4}$ has all electrons paired (N-N bonded) and is diamagnetic and colourless; only $\mathrm{NO_2}$ is paramagnetic. Hence I, II and III.