Choose the correct metal/ ion from the brackets which ..........
A. has chemical reactivity similar to that of the first few members of the Lanthanoids \((\mathrm{Zn}, \mathrm{Ca}, \mathrm{Fe}, \mathrm{Cu})\).
B. has stable \(4 \mathrm{f}^7\) electronic configuration, but acts as a strong reducing agent and converts to \(\mathrm{M}^{3+}\) state. \(\left(\mathrm{Eu}^{2+}, \mathrm{Ce}^{2+}, \mathrm{Pr}^{2+}, \mathrm{Dy}^{2+}\right)\)
C. is a colorless ion \(\left(\mathrm{Tm}^{3+}, \mathrm{Lu}^{3+}, \mathrm{Gd}^{3+}, \mathrm{Sm}^{3+}\right)\).
D. shows stable +2 oxidation state and is diamagnetic \((\mathrm{Ce}, \mathrm{Sm}, \mathrm{Ho}, \mathrm{Yb})\)

1. A \(\mathrm{A}: \mathrm{Zn} \quad \mathrm{B}: \mathrm{Ce}^{2+}, \quad \mathrm{C}:\mathrm{Gd}^{3+} \quad \mathrm{D}: \mathrm{Sm}\)
2. B \(\mathrm{A}: \mathrm{Ca} \quad \mathrm{B}: \mathrm{Eu}^{2+}
   \quad \mathrm{C}: \mathrm{Lu}^{3+}
   \quad \mathrm{D}: ~ \mathrm{Yb}\)
3. C \(\mathrm{A}: \mathrm{Fe} \quad \mathrm{B}: \mathrm{Pr}^{2+}
   \quad \mathrm{C}: \mathrm{Tm}^{3+}
   \quad \mathrm{D}: ~ \mathrm{Ce}\)
4. D \(\mathrm{A}: \mathrm{Cu} \quad \mathrm{B}: \mathrm{Dy}^{2+}
   \quad \mathrm{C}: \mathrm{Sm}^{3+}
   \quad \mathrm{D}: ~ \mathrm{Ho}\)