Variation of acceleration due to gravity ($g$) with distance $x$ from the centre of the Erath is best represented by ( $R\to$ Radius of the Earth)

The value of g is maximum at the surface of the Earth and $g=0$ at centre of the Earth. If one goes away from the Earth surface, again the value of g decreases.

Thus, graph $\left(d\right)$ is showing the correct variation of g.