The intensity of the gravitational field ($E$) or acceleration due to gravity ($g$) varies with distance $r$ from the centre of the Earth:

1. Inside the Earth ($r < R$): Assuming uniform density, the field is directly proportional to the distance from the centre. $E = \frac{GM}{R^3}r$, so $E \propto r$. This is represented by a straight line passing through the origin.
2. At the surface ($r = R$): The field reaches its maximum value, $E = \frac{GM}{R^2}$.
3. Outside the Earth ($r > R$): The field behaves as if the entire mass is concentrated at the centre and follows the inverse square law. $E = \frac{GM}{r^2}$, so $E \propto \frac{1}{r^2}$. This is represented by a rectangular hyperbola decreasing as $r$ increases. Therefore, the correct graph shows a linear increase up to $r=R$ followed by a curvilinear decrease.