A function f is defined on interval (0, 1) as follows when x is irrational f(x)=1 when x is rational no.and lcm(p, q) =1, then which one of the follow

A function f is defined on interval (0, 1) as follows when x is irrational f(x)=1 when x is rational no.and lcm(p, q) =1, then which one of the following is true? (A) f is continuous at each irrational point and discontinuous at each rational point. (B) f is continuous at each rational point and discontinuous at each irrational point. (C) f is discontinuous at each rational and irrational points. (D) f is continuous at each rational and irrational points