(a)Sharp transition and fluorescence in lanthanides
(b)Broad bands and d-d transitions
(c)Very high spin-orbit coupling and transition elements
(d)Charge transfer and molar absorptivity of the order of $10^{1} \mathrm{L} \mathrm{mol}^{-1} \mathrm{cm}^{-1}$
Answer
Answer: C ✓ checked by 4AB · confidence medium
Explanation
Very large spin–orbit coupling is a feature of lanthanides/actinides, not of the 3d transition elements; the other pairings (sharp f–f lines, broad d–d bands, intense charge transfer with ε ~10⁴) are correct.