All of the following statements are correct except

• A

  The total length of an astronomical telescope is the sum of the focal lengths of its two lenses

• B

  The image formed by the astronomical telescope is always erect because the effect of the combination of the two lenses is divergent

• C

  The magnification of an astronomical telescope can be increased by decreasing the focal length of the eye-piece

• D

  The magnifying power of the refracting type of astronomical telescope is the ratio of the focal length of the objective to that of the eye-piece