An ionic bond is the attraction between

a. similarly charged ions.

b. oppositely charged ions.

c. neutral ions.

d. neutral atoms.

The answer would be : b. oppositely charged ions.

Hope this helps !

Photon

The answer should be c.

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.