The covalent bond with the greatest polarity would form in which of the atom pairs below? A. Br - Br
B. S - O
C. C - P
D. C - O
E. B - O

The answer is b because I know the answer

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.