Let $V$ be the set of vertices of a regular polygon with twenty sides. Three distinct vertices are chosen at random from $V$. Then, the probability that the chosen triplet are the vertices of a right angled triangle is\\
(A) $\frac{7}{19}$\\
(B) $\frac{3}{19}$\\
(C) $\frac{3}{38}$\\
(D) $\frac{1}{38}$.