(c)
Given, $\frac{dx}{dt} = \cos^{2}{\pi x}$
On differentiating $w.r.t.x$, we get
$\frac{d^{2}x}{dt^{2}} = - 2\pi\sin{2\pi x =}$ negative
The particle never reaches the point, it means
$\frac{d^{2}x}{dt^{2}} = 0\ \Rightarrow \ - 2\pi\sin{2\pi x =}0$
$\Rightarrow \sin{2\pi x = \sin\pi}$
$\Rightarrow 2\pi x = \pi\ \Rightarrow x = \frac{1}{2}\$
The particle never reaches at $x = \frac{1}{2}$