NEET UG CHEMISTRY MCQ: d & f- BLOCK ELEMENTS

Option D ($\mathrm{[Xe]4}{\mathrm{f}^\mathrm{7}}\mathrm{6}{\mathrm{s}^\mathrm{2}},\,\mathrm{[Xe]4}{\mathrm{f}^\mathrm{7}}\mathrm{5}{\mathrm{d}^\mathrm{1}}\mathrm{6}{\mathrm{s}^\mathrm{2}}\,\mathrm{and}\,\mathrm{[Xe]4}{\mathrm{f}^9}\mathrm{6}{\mathrm{s}^\mathrm{2}}$) is correct because it represents the correct electronic configurations of Eu, Gd, and Tb, considering Hund's rule and stability of half-filled orbitals.