Question

# The period of the function:$f(x) = \left\{ {\begin{array}{*{20}{c}}{1,}&{x{\text{ is rational}}}\\{0,}&{x{\text{ is irrational}}}\end{array}\;\;\;\;\;is} \right.$A.1B.2C.non-periodicD.periodic but having no fundamental period

$f(x) = \left\{ {\begin{array}{*{20}{c}} {1,}&{x{\text{ is rational}}}\\ {0,}&{x{\text{ is irrational}}} \end{array}\;\;\;\;\;is} \right.$