Acceleration Due to Gravity question from NEET 2017

Answer: (c)

1. For $h \ll R$: $g_h = g\left(1 - \frac{2h}{R}\right)$ and $g_d = g\left(1 - \frac{d}{R}\right)$.
2. Equal $g$: $\frac{2h}{R} = \frac{d}{R} \Rightarrow d = 2h = 2\text{ km}$
3. So the answer is (c) $d = 2\text{ km}$.