If $7 \sin^2 \theta + 3 \cos^2 \theta = 4,$ then $\tan \theta=$

Question

$\begin{array}{1 1} (a)\; \sqrt{3}\\(b)\; -\sqrt{3}\\ (c)\; \frac{-1}{\sqrt{3}} \\ (d)\; \frac{1}{\sqrt 3 } \end{array}$