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GATE 2022 MA – Question 23

Topology · Topological Spaces and Constructions · 1 mark · Multiple choice

Let p:[0,1]→{0,1} be the indicator of [1/2,1], with the usual interval topology and its induced quotient topology on {0,1}. Which holds?

  1. Open but not closed
  2. Closed but not open
  3. Both open and closed
  4. Neither open nor closed

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Correct answer: (D) Neither open nor closed

Explanation

The quotient opens are ∅,{0},{0,1}, since p⁻¹({0})=[0,1/2) is open but p⁻¹({1}) is not. The open interval (1/2,3/4) maps to {1}, which is not open. The closed singleton {0} in the domain maps to {0}, which is not closed in the quotient. **D**.

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