The acceleration due to gravity on the surface of the Earth is maximum

The acceleration due to gravity on the surface of the Earth is maximum and it

increases as we go up
decreases as we go up or down
increases as we go down
neither increases nor decreases as we go up or down
This question was previously asked in
UPSC CAPF – 2011
The acceleration due to gravity on the surface of the Earth is maximum, and it decreases as we go up or down.
The acceleration due to gravity (g) at a distance r from the center of the Earth (mass M) is given by g = GM/r². On the surface, r is the Earth’s radius (R), so g_surface = GM/R². As we go up, r increases (r = R + altitude), so g decreases according to the inverse square law. As we go down into the Earth, the mass (M) pulling us decreases (only the mass within the sphere of radius r contributes to the gravitational force at radius r, assuming uniform density for simplicity, though density varies in reality), while the distance from the center (r) decreases. The effect of decreasing mass outweighs the effect of decreasing distance, causing gravity to decrease linearly towards the center (g = GM_r/r², where M_r is the mass within radius r). Gravity is zero at the Earth’s center.
Therefore, gravity is maximum at the surface and decreases both above and below the surface. Minor variations exist due to altitude, latitude (Earth’s bulge), and local geological variations, but the general trend is decrease away from the surface.