If $s\mathit{-}p$ mixing does not occur in ${\mathrm{B}}_2$ molecule, then which of the following must be false for this molecule? (Assume $Z$-axis as internuclear axis)

The molecule is not paramagnetic.

The axis that joins the nuclei of atoms bound to one another in a molecule is known as the bond axis or internuclear axis. Any axis can be used as an internuclear axis; however, if the z axis is used, there is zero overlap between the s and the px, py, or pz orbitals.

Total number of electrons = 10 for ${\mathrm{B}}_2$

$(\sigma ,1s{)}^2{\left({\sigma }^{\ast }1s\right)}^2(\sigma 2s{)}^2{\left({\sigma }^{\ast }2s\right)}^2={\left(\sigma 2P_z\right)}^2$

Here, Bond order is 1.

Hence, the correct option is A