the force between the earth and the body which is at a distance r from the center of the earth is F. What must be this distance for the force to be doubled.

Explanation:

The gravitational force between the earth and another body is F = -GM_em/r^2 r where G = 6.67 times 10^-11 Nm^2/kg^2 is the gravitational constant, M_e = 5.97 times 10^24 kg is the mass of the earth, m is the mass of the other body, and r is the position vector of the second body with respect to the centre of the earth.

object 2 because all the other ones are wrong