19. Among the [M(H₂O)₆]ⁿ(aq) (M: 3d -transition metal ion) complexes, why is the [Mn(H₂O)₆]²⁺ shows the much weaker UV-Vis absorption than solution of other metal ions? (A) because other transition metal ions (B) because Mn²⁺ is high-spin d⁵ but other transition metal ions are low-spin (C) because the UV-Vis absorption of other transition metal ions are parity-allowed (D) because there are no excited states of the same spin multiplicity and no spin-allowed absorption (E) None of the above is correct