The acceleration due to gravity at a height 1 km above the earth is the same as at a depth d below the surface of earth. Then:

The correct option is A
d=2km
Acceteration due to gravity at height h, gn=g0(1−h/R)
h=1km
Acceleration due to gravity at depth d, gd=g0(1−d/R)
gh=gd
g0(1−h/R)=g0(1−d/R)→d=2h=2×1km
d=2km