Displacement describes how far and in what direction an object has moved
relative to its starting point.
a. true
b. false

This is true. The displacement does not take into account the path taken but rather the start and end point.

False. Displacement does not describe the direction. Displacement only describes a scalar unit of length

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.