<br> $AB$ is a chord in a circle whose centre is $'O'$. The radius of the circle is 8 cm. The distance of the chord from its centre is 6 cm. Then the length of the chord is

Question

$\begin{array}{1 1} (a)\; 2\sqrt{7} \\ (b)\; 3 \sqrt{7} \\ (c)\; 4 \sqrt{7} \\ (d)\; 8\sqrt{7} \end{array}$