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Which of these is true?

1) Given a topology T and basis B, a set U is open iff for every x in U there exists basis element B with x belonging to B, and B contained in U.

2) Given a topology T and basis B, a set U is open iff for every x in U there exists open set V with x belonging to V, and V contained in U.

3) Given a topology T and basis B, a set U is open iff exery point of U belongs to the closure of U.

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# 3 easy topology questions.

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