For and the correct choice is :
(A) is diabasic and reducing agent.
(B) is diabasic and non-reducing agent.
(C) is tribasic and reducing agent.
(D) is tribasic and non- reducing agent.
Oxidation state of P is + 3 can be decrease to – 3 and increase to + 5. Hence it can act as both
reducing as well as oxidising agent.