Correct Answer - D
Nitric acid acts as an oxidising agent while reacting with copper. When dil `HNO_(3)` reacts, reaction proceeds as:
`3Cu+8HNO_(3)(dil). To 3Cu(NO_(3))_(2)+2NO+4H_(2)O`.
and when conc. `HNO_(3)` is used, reaction proceeds as and `Cu+4HNO_(3) ("conc") to Cu(NO_(3))_(2)+2NO+4H_(2)O` and when conc. `HNO_(3)` is used, reactio proceeds as
`Cu+4HNO_(3)("conc") to Cu(NO_(3))_(2) + 2NO_(2)+2H_(2)O`