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The Dirichlet function, the indicator of the rationals, is continuous at how many points?
Aevery irrational number
Bno point of the line
Cexactly one point
Devery rational number
Answer & Solution
Correct answer: B. no point of the line
Every interval holds both rationals and irrationals, so the function jumps between 0 and 1 near each point.
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