Given that we need to find the eccentricity of the ellipse whose minor axis is equal to the distance between the foci.

We know that distance between foci is 2ae and length of minor axis is 2b.

⇒ 2ae = 2b

⇒ b = ae

⇒ b² = a²e²

We know that b² = a²(1 - e²)

⇒ a²(1 - e²) = a²e²

⇒ a² = 2a²e²

⇒

⇒

∴ The correct option is C