The function $f(x)=\left(4 \sin ^{2} x-1\right)^{n}\left(e^{x}-x+1\right)$
$\mathrm{n} \in \mathrm{N}$, has a local minimum at $\mathrm{x}=\frac{\pi}{6}$, then
(A) n can be any even natural number
(B) $\mathrm{n}$ can be an odd natural number
(C) $\mathrm{n}$ can be odd prime number
(D) n can be any natural number