Correct statement(s) among the following is/are :
A. Solid `PCl_(5)` exists are tetrahedral `[PCl_(4)]^(+)` and octahedral `[PCl_(6)]^(-)` ions
B. Solid `PBr_(5)` exists as `[PBr_(4)]^(+) Br^(-)`
C. Cold, dilute `HNO_(3)` on reaction with copper gives nitric oxide
D. Oxides of phosphorous exist as monomers