Identify Oxoacids of Phosphorus Containing Direct Phosphorus Hydrogen Bonds

To determine which of the given oxoacids of phosphorus contain direct $\text{P}-\text{H}$ bonds, we analyze their chemical structures:

1. $\text{H}_3\text{PO}_4$ (Orthophosphoric acid):

   • The central phosphorus atom is bonded to one oxygen atom via a double bond ($\text{P}=\text{O}$) and three hydroxyl groups via single bonds ($\text{P}-\text{OH}$).
   • Structural representation: $\text{O}=\text{P}(\text{OH})_3$
   • Number of $\text{P}-\text{H}$ bonds = $0$.

2. $\text{H}_3\text{PO}_3$ (Orthophosphorous acid / Phosphonic acid):

   • The central phosphorus atom is bonded to one oxygen atom via a double bond ($\text{P}=\text{O}$), two hydroxyl groups ($\text{P}-\text{OH}$), and one hydrogen atom directly ($\text{P}-\text{H}$).
   • Structural representation: $\text{H}-\text{P}(=\text{O})(\text{OH})_2$
   • Number of $\text{P}-\text{H}$ bonds = $1$.

3. $\text{H}_4\text{P}_2\text{O}_7$ (Pyrophosphoric acid):

   • It contains a $\text{P}-\text{O}-\text{P}$ linkage where each phosphorus atom is bonded to one oxygen atom via a double bond ($\text{P}=\text{O}$) and two hydroxyl groups ($\text{P}-\text{OH}$).
   • Structural representation: $(\text{HO})_2(\text{O})\text{P}-\text{O}-\text{P}(\text{O})(\text{OH})_2$
   • Number of $\text{P}-\text{H}$ bonds = $0$.

4. $\text{H}_3\text{PO}_2$ (Hypophosphorous acid / Phosphinic acid):

   • The central phosphorus atom is bonded to one oxygen atom via a double bond ($\text{P}=\text{O}$), one hydroxyl group ($\text{P}-\text{OH}$), and two hydrogen atoms directly ($\text{P}-\text{H}$).
   • Structural representation: $\text{H}_2\text{P}(=\text{O})(\text{OH})$
   • Number of $\text{P}-\text{H}$ bonds = $2$.

Thus, the compounds containing $\text{P}-\text{H}$ bond(s) are $\text{H}_3\text{PO}_3$ and $\text{H}_3\text{PO}_2$.

Correct Options: B and D