Electric Flux & Gauss's Law question from JEE Main 2019 (11 Jan, Shift 1)

Answer: (d)

1. The graph is constant for $r < r_0$ and falls as $\frac{1}{r}$ for $r > r_0$.
2. Field of a shell is zero inside (not a nonzero constant); field of a sphere rises linearly inside. Neither fits.
3. Potential of a solid sphere varies (parabolically) inside, so it is not flat.
4. Potential of a shell is $\frac{kQ}{r_0}$ (constant) inside and $\frac{kQ}{r}$ outside, which matches.
5. So the answer is (d) potential of a uniformly charged spherical shell.