The length of the latus rectum of an ellipse is $\large\frac{1}{3}$ of the major axis. It's $e$ is :

Question

\[(a)\;\frac{2}{3} \quad (b)\;\sqrt {\frac{2}{3}} \quad (c)\;\frac{5.4.3}{7^3} \quad (d)\;\bigg(\frac{3}{4}\bigg)^4\]