`H_(3)PO_(4) overset(Delta)rarr X overset(Delta)rarrY` gives a white precipitate with silver nitrate solution.
Y can form polyanions. The one that represents the polyanion is:
A. `P_(3)O_(9)^(3-)`
B. `P_(2)O_(7)^(2-)`
C. `P_(4)O_(13)^(6-)`
D. `P_(3)O_(10)^(5-)`