We consider the function $f$ defined on $] 0 ; + \infty [$ by

$$f ( x ) = \frac { 1 } { x } ( 1 + \ln x )$$

\begin{enumerate}
  \item In the three situations below, we have drawn, in an orthonormal coordinate system, the representative curve $\mathscr { C } _ { f }$ of the function $f$ and a curve $\mathscr { C } _ { F }$. In only one situation, the curve $\mathscr { C } _ { F }$ is the representative curve of a primitive $F$ of the function $f$. Which one? Justify the answer.
\end{enumerate}