F maps (0,1) -> [0,1]. f(x)=0 if x is irrational and 1/q if x is rational with reduced form p/q, for p & q relatively prime integers. Which of the following is correct?
a) f is discontinuous at all rational numbers in (0,1)
b) f is continuous at all irrational numbers in (0,1)
c) f is continuous at all rational numbers in (0,1)
d) f is discontinuous at all irrational numbers in (0,1)