Light incident on a surface at an angle of 45° undergoes diffused reflection. At what angle will it reflect?
A. only at angles less than 45º
B. only at angles greater than 45°
C. only at 45°
D. at any angle between -90° and 90°
E. only at 0°

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.

Yeah, but what are you trying to ask?