24P1Q11

11 A

$\displaystyle \phi =-\frac{GM}{r}$ . So the “magnitude of gravitational potential” refers to the $\displaystyle \frac{GM}{r}$ term. As r increases, this magnitude decreases.
From the curvature of the graph, it is clear that the difference between the gravitational potentials of P and Q also decreases as they move towards infinity.