In ruby and emerald,the metal ion$(s)$ present is/are

Which of the following imparts green colour to the glass?

Alkaline oxidative fusion of $MnO_2$ gives $A$ which on electrolytic oxidation in alkaline solution produces $B$. $A$ and $B$ respectively are:

$X + H^{+} \rightarrow Y + Na^{+} + H_2O$
$Y + KCl \rightarrow K_2Cr_2O_7 + NaCl$
Identify $X$ and $Y$ in the given reactions.

The fusion of chromite ore with sodium carbonate in the presence of air leads to the formation of products $A$ and $B$ along with the evolution of $CO_2$. The sum of spin-only magnetic moment values of $A$ and $B$ is .......... $B.M.$ (Nearest integer)
(Given atomic number: $C: 6, Na: 11, O: 8, Fe: 26, Cr: 24$)

Mark the correct statements.