2026 CSAT, all questions

UPSC Prelims 2026 · CSAT

Question 67: Logical Reasoning and Mental Ability

If ZERO is encoded as ADSN, then how do you encode STOP?

aSPOT
bTSPO
cTSOP
dPOST

AnswerUPSC’s answer is (b).

Compare ZERO with ADSN letter by letter: Z to A is one step forward, E to D one step back, R to S one step forward, O to N one step back. The pattern is +1, −1, +1, −1. Apply it to STOP: S + 1 = T, T − 1 = S, O + 1 = P, P − 1 = O. The code is TSPO.

Why each option is right or wrong
  • (a) Wrong: SPOT does not follow the +1, −1 pattern.
  • (b) Right: T, S, P, O.
  • (c) Wrong: the third and fourth letters should be P and O, not O and P.
  • (d) Wrong: POST does not follow the shift pattern.

Only the provisional key (27 May 2026) was found; the final key replaces it when found.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2026, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.