a b c d

d

$\text{Power of Objective lens of telescope = 0.5 D}$  $\Rightarrow \text{focal length of objective lens of telescope }f_0 = 200 cm$ $\text{Power of Eye lens of telescope = 20 D }$ $\Rightarrow \text{ focal length of eyepiece of telescope } f_e = 5 cm$ $\text{Magnification of the telescope M } = \frac{f_0}{f_e} = 40$