Which graph correctly presents the variation of acceleration due to gravity with distance from the centre of the earth?

${\mathrm{g}}_{\mathrm{d}} = \mathrm{g}(1-\frac{\mathrm{d}}{\mathrm{g}})$

or ${\mathrm{g}}_{\mathrm{d}} = \mathrm{g}\frac{\mathrm{R}-\mathrm{d}}{\mathrm{R}}$

or ${\mathrm{g}}_{\mathrm{d}} = \frac{\mathrm{gy}}{\mathrm{R}}\mathrm{or} {\mathrm{g}}_{\mathrm{d}} \propto \mathrm{y}$

So, within the Earth, the acceleration due to gravity varies linearly, with the distance from the centre of the Earth. This explains the linear portion OA of the graphs.