The eccentricity of the ellipse of minor-axis $2 b$, if the line segment joining the foci subtend an angle $2 \alpha$ at the upper vertex is equal to

• A

  $\cos \alpha$
• Correct answer
  B

  $\sin \alpha$
• C

  $\tan \alpha$
• D

  $\sec \alpha$

Hence, the correct answer is option: 'B'.