A set contains 7 elements . A non - empty subset A of S and an element x of S are chosen at random . Then the probability that $\; x \in A\;$ is :

Question

$(a)\;\large\frac{1}{2} \qquad(b)\;\large\frac{64}{127}\qquad(c)\;\large\frac{63}{128}\qquad(d)\;\large\frac{31}{128} $