A crystal is a solid (or liquid) in which the constituent atoms, molecules, or ions are packed to have a as well as a short range order

long range order

Explanation:

A crystal consists of atoms, ions or molecules having both short range and long range order. The atoms, ions or molecules are arranged in a regular pattern throughout the lattice both at immediate vicinities and across the entire crystal structure.

This order accounts for the definite shape and unique properties of crystals which include their sharp melting and boiling points which distinguishes them from amorphous substances.

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

i think it's letter a.