Analyzing each option's variation with $r$:

• Electric field of solid sphere: increases linearly inside ($\propto r$), decreases as $1/r^2$ outside.
• Potential of spherical shell: constant inside (= $kQ/R$), decreases as $1/r$ outside. This matches the graph exactly.
• Potential of solid sphere: varies parabolically inside, $\propto 1/r$ outside — not constant inside.
• Electric field of spherical shell: zero inside, $1/r^2$ outside.

The graph (constant inside, $1/r$ decrease outside) matches the potential of a uniformly charged spherical shell.