Dinitrogen pentoxide ,a colourless deliquescentsolid is ,prepared by
A. heating `NH_(2)NO_(2)` with an excess of oxygen
B. dehydrating `HNO_(2)` with CaO
C. dehydrating `HNO_(3)` with `P_(4)O_(10)`
D. heating a mixture of `HNO_(2)" and "Ca(NO_(3))_(2)`
