c) Show that, if $f\in \mathcal{D}'(\Bbb R)$ satisfies $f'=0$, then $f$ is a regular distribution associated with a constant function.
I know how this question is solved:
Can anyone suggest possible alternatives/variations of this question, i.e. similar exercises to the one above?
A harder question is to show that every distribution $T$ on an open interval $I$ admits a primitive, that is a distribution $S$ on $I$ such that $S^\prime = T$.