The length of an astronomical telescope for normal vision (relaxed eye) (f_o = focal length of objective lens and f_e  = focal length of eye lens) is

• A

  ${\mathrm{f}}_0\times {\mathrm{f}}_{\mathrm{e}}$

• B

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

• C

  ${\mathrm{f}}_0+{\mathrm{f}}_{\mathrm{e}}$

• D

  ${\mathrm{f}}_0-{\mathrm{f}}_{\mathrm{e}}$