There are two equations for the reaction of copper with nitric acid. It depends on whether the nitric acid is concentrated or not.
If it is concentrated and in excess then the ratio is 1:4 copper to nitric acid. If it is dilute then the ratio is 3:8.
For example, copper reacts with DILUTE nitric acid at ambient temperatures with a 3:8 stoichiometry.
$(A) 3Cu + 8HNO_3 –> 3Cu(NO_3)_2 + 2NO + 4H_2O$ which is the answer
$(B) Cu + 4HNO_3 –> Cu(NO_3)_2 + 2NO + 2H_2O$ is the reaction with CONCENTRATED Nitric acid.