I have doubt in this answer,
Unfortunately, the choice $e^{1/e}$ was not given. The two values of $x$ that you are given that bracket $e$ are $2$ and $3$, so the correct choice is either $2^{1/2}$ or $3^{1/3}$.
How does one prove that if we extrapolate a sequence $a_n$ as a function $f(x)$ and extrema of $f(x)$ occurs at $x=j$ ( $j \in [0, \infty]$) then the extrema of the sequence occurs at the whole numbers which bracket $j$?