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Daily practice

The Daily Trap

One Part C question, the same one for everyone, every morning. Four statements, four true-or-false calls — and like the real paper, only the exact correct set scores. No account, no sign-up.

Daily Trap · No. 52

Topology › Connectedness and components

Let X be a topological space and, for x ∈ X, let C(x) denote the connected component of x. Which of the following are true?

C(x) is always closed in X.

All four count. Part C scores only for the exact correct set.

Why one wrong call costs the whole question

Part C is worth 4.75 marks a question with no negative marking, and you may attempt 20 of the 60. What makes it hard is the rule underneath: credit only for selecting exactly the right set of options. A question you are three-quarters sure of pays the same as one you did not read — which is why judging statements one at a time is the skill worth practising, and why this puzzle marks them that way.