The greatest acceleration or deceleration that a train may have is $\alpha$ .The minimum time in which the train can get from one station to the next at a distance S is

Question

$\begin{array}{1 1}(A)\;\large\frac{S}{a} \\(B)\;\large\frac{2S}{a}\\(C)\;2\sqrt{\large\frac{S}{a}}\\(D)\;\sqrt {\large\frac{S}{2a}} \end{array} $