Answer & explanation
Correct answer: option 2
$\text{Flux passing through the sphere of radius a } \phi = E 4\pi a^2 = k 4\pi a^3$
$ \phi = \frac{q_{in}}{\epsilon_0} = k4\pi a^3$
$ q_{in} = k 4\pi \epsilon_0 a^3$
Correct answer: option 2
$\text{Flux passing through the sphere of radius a } \phi = E 4\pi a^2 = k 4\pi a^3$
$ \phi = \frac{q_{in}}{\epsilon_0} = k4\pi a^3$
$ q_{in} = k 4\pi \epsilon_0 a^3$