If a reaction occurs, what will be the products of the unbalanced reaction below? Cu(s) + Ni(NO3)2(aq)

The Activity Series of Elements
A.
CuNi(NO3)4(s)
B.
Ni(s) + Cu(NO3)2(aq)
C.
No reaction will occur.
D.
CuNi(s) + NO2(g)

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.