JEE Main 2022 · 26 Jun · Shift 1, Chemistry question 71

Eliminate. White $\mathrm{P_4}$ with alkali gives $\mathrm{PH_3}$ and hypophosphite, $\mathrm{H_2PO_2^-}$ (two P-H bonds). $\mathrm{P_2O_3}$ and $\mathrm{H_3PO_3}$ give phosphite, $\mathrm{HPO_3^{2-}}$ (one P-H bond).

Keyed answer. That leaves red phosphorus, which NTA's key gives; its product is taken as an oxoacid without a P-H bond.

(B)