Correct Answer - B
`NO_(3)^(-)` and `NO_(2)^(-)` both give brown ring test and reduction of `NO_(3)^(-)` and `NO_(2)^(-)` both give ammonia which with dilute `HCl` gives dense white fumes.
if `NH_(4)NO_(3)overset(Delta)toN_(2)O+2H_(2)O,N_(2)O` supports the combustion
but `NH_(4)NO_(2)overset(Delta)toN_(2)+2H_(2)O`Nitrogen does not supports combustion.
Hence, the anion is `NO_(3)^(-)`.