JEE Math Practice Question

Let S = $$\left\{ {\left( {x,y} \right) \in {R^2}:{{{y^2}} \over {1 + r}} - {{{x^2}} \over {1 - r}}} \right\};r \ne \pm 1.$$ Then S represents :

1. A.an ellipse whose eccentricity is $${1 \over {\sqrt {r + 1} }},$$ where r > 1
2. B.an ellipse whose eccentricity is $${2 \over {\sqrt {r + 1} }},$$ where 0 < r < 1
3. C.an ellipse whose eccentricity is $${2 \over {\sqrt {r - 1} }},$$ where 0 < r < 1
4. D.an ellipse whose eccentricity is $$\sqrt {{2 \over {r + 1}}}$$, where r > 1