The transition metal ions responsible for color in ruby and emerald are, respectively :

Question

$\begin{array}{1 1} (1)\; Cr^{3+} \;and\; Co^{3+} \\ (2)\; Co^{3+}\; and\; Cr^{3+} \\ (3)\; Co^{3+}\; and\; Co^{3+} \\ (4)\; Cr^{3+}\; and\; Cr^{3+} \end{array} $