If F_o and F_e are the focal length of the objective and eye-piece respectively of a telescope, then its magnifying power will be 

• A

  ${\mathrm{F}}_{\mathrm{o}}+{\mathrm{F}}_{\mathrm{e}}$

• B

  ${\mathrm{F}}_{\mathrm{o}}\times {\mathrm{F}}_{\mathrm{e}}$

• C

  $\frac{{\mathrm{F}}_{\mathrm{o}}}{{\mathrm{F}}_{\mathrm{e}}}$

• D

  $\frac{1}{2}\left({\mathrm{F}}_{\mathrm{o}}+{\mathrm{F}}_{\mathrm{e}}\right)$