Choose the statements which are incorrect in the case of Lanthanoids.
A. \(\mathrm{Ce}^{4+}\) is diamagnetic while \(\mathrm{Sm}^{3+}\) is paramagnetic.
B. The atomic size of the transition metals having atomic number greater than 71 are very close to that of the elements above them.
C. Lanthanoids react with hot water forming water soluble \(\mathrm{Ln}(\mathrm{OH})_3\) with the liberation of \(\mathrm{O}_2\).
D. The general electronic configuration of Lanthanoids is \((n-2) f^{1-14} 5 d^0 6 s^2\), where \(n=6\).

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.