option A
Explanation-
Phosphorus can easily assume +5 oxidation state in compounds due to the presence of unfilled 3d-orbitals. For example, PCl3 (O.S. +3) and PCl5 (O.S. +5) are ...
option A
Due to presence of vacant d orbitals in P, electons present in 3 p can excites to vacant 3 d orbitals, so its valency is 5 so P can form R3P=O.
Whereas due to absence of...