Which of the following statements is not true about `H_(3)PO_(2)` ?
A. It is a tribasic acid
B. One mole of it is neutralised by 0.5 mole of `Ca(OH)_(2)`
C. `NaH_(2)PO_(2)` is not an acidic salt
D. It disproportionates to `H_(3)PO_(3) " and " PH_(3)` on heating
