The lanthanoid that does NOT show +4 oxidation state is :

The correct electronic configuration and spin-only
magnetic moment (BM) of Gd³⁺ (Z = 64), respectively, are :

In the sixth period, the orbitals that are filled are :

The incorrect statement(s) among (a) - (c) is (are)

(a) W(VI) is more stable than Cr(VI).

(b) In the presence of HCl, permanganate titrations provide satisfactory results.

(c) Some lanthanoid oxides can be used as phosphors.