(I) H3PO2 , (II) H3PO3 (III) H3PO4Correct increasing order of acidic strength () is

structure of conjugate bases of  I , II , III respectively                                                                                      (A)                                        (B)                                         (C)Consider  (A)                                              Equivalent (indistinguishable) structures                   maximum dispersal of negative chargeconsider   (B) :     possibility (I)     Possibility (II)  Thus structure (B) is less stable as compared to (A)Consider (C) :   possibility (I)  Possibility (II)                         Possibility (III)                           (C) is much more unstableThus stability of H3PO2- > H2PO3- > H2PO4-Other explanation:-I effect of P=O group is distributed only on one -OH in H3PO2 where as on two -OH groups in H3PO3And three -OH groups in H3PO4