The d-orbital which is not involved in  ${\mathrm{sp}}^3{\mathrm{d}}^3$ hybridisation in pentagonal bipyramidal geometry is:

The d-orbital  is not involved in  ${\mathrm{sp}}^3{\mathrm{d}}^3$ hybridisation in pentagonal bipyramidal geometry is:$s+p_x+p_y+p_z+d_{xy}+d_{x^2-y^2}+d_z$.

Thus, the correct option is d.