Lecture 7 (Topology)

Let X = {a, b, c}. Which of the following collections is a topology on X?

1. A.{ ∅, {a}, {b}, {a, b, c} }
2. B.{ {a}, {b}, {c}, {a, b, c} }
3. C.{ ∅, {a, b}, {b, c}, {a, b, c} }
4. D.{ ∅, {a}, {a, b}, {a, b, c} }