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Let X be a locally connected topological space. Then which of the following is true ?

  • A.X is connected
  • B.X is locally path connected
  • C.Every component of an open set of X is open in X
  • D.Every component of X is also a path component of X

Answer: C

The true statement is every component of an open set of X is open in X.

This is a standard characterisation: X is locally connected if and only if the components of every open subset are open. If U is open and C is a component of U, each point of C has a connected open neighbourhood inside U, which must lie in C, so C is open.

Local connectedness does not imply connectedness (two disjoint intervals are locally connected but not connected). Nor does it give local path connectedness or make components path components: Kirch's topology on the positive integers is a countable, connected, locally connected Hausdorff space, and a countable Hausdorff space has no non-constant paths, so its single component is not path connected.

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