The correct answer is (A): Ce(At. No. 58)
Explanation:
Ce → [Xe]4f1 5d1 6s2
Ce+4 → [xe] 4f° 5d° 6s°
Cerium in +4 oxidation state acquires inert gas configuration.
Method used for separation of mixture of products (B and C) obtained in the following reaction is: 
In the given figure, the blocks $A$, $B$ and $C$ weigh $4\,\text{kg}$, $6\,\text{kg}$ and $8\,\text{kg}$ respectively. The coefficient of sliding friction between any two surfaces is $0.5$. The force $\vec{F}$ required to slide the block $C$ with constant speed is ___ N.
(Given: $g = 10\,\text{m s}^{-2}$) 