चार कथन X, Y, Z और W हैं। उनके संबंधों का वर्णन निम्नलिखित है :
यदि X गलत है, तो Z भी गलत है; यदि Y गलत है, तो W सही है; यदि W सही है, तो X गलत है।
निम्नलिखित में से कौन-सा/कौन-से सही है/हैं?
- I.यदि X सही है, तो Y भी सही है।
- II.यदि Z सही है, तो यह आवश्यक नहीं है कि Y सही है।
नीचे दिए गए कूट का प्रयोग कर उत्तर चुनिए।
Read this question in English
There are four statements X, Y, Z and W. Their relations are as follows:
If X is incorrect, then so is Z; if Y is incorrect, then W is correct; if W is correct, then X is incorrect.
Which of the following is/are correct?
I. If X is correct, then so is Y.
II. If Z is correct, then it is not necessary that Y is correct.
Select the answer using the code given below.
(a) I only · (b) II only · (c) Both I and II · (d) Neither I nor II
उत्तर और व्याख्या · explanation in English
Answer: (a) केवल I
Flip each rule into its contrapositive: Z correct → X correct → W incorrect → Y correct. So X correct forces Y correct (I holds), and Z correct also forces Y correct, which makes II wrong.
- Rule 1: X incorrect → Z incorrect; contrapositive: Z correct → X correct.
- Rule 3: W correct → X incorrect; contrapositive: X correct → W incorrect.
- Rule 2: Y incorrect → W correct; contrapositive: W incorrect → Y correct.
- Chain: Z correct → X correct → W incorrect → Y correct.
- I: X correct → Y correct — true. II: Z correct forces Y correct, so 'not necessary' is false.
- ✓ I X correct → W incorrect (rule 3) → Y correct (rule 2).
- ✗ II Z correct → X correct (rule 1) → Y correct; so Y is necessarily correct.
Remember · 'If P then Q' equals 'if not Q then not P'. Rewrite each rule this way and chain them.
Question and answer: UPSC's provisional GS Paper II (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·