Paper 1 · Logical Reasoning
UGC NET December 2023 (14.12.2023) Shift-I
Which of the following statements are so related that they cannot both be true, nor can they both be false? Choose the correct answer from the options given below.
- 1. All mammals are vertebrates
- 2. Some mammals are vertebrates
- 3. Some mammals are not vertebrates
- 4. No mammals are vertebrates
A1 and 2 only
B2 and 4 only ✓ Correct
C3 and 4 only
D1 and 4 only
Correct answer: (B) 2 and 4 only — The contradictory pair is some mammals are vertebrates and no mammals are vertebrates, so the answer is 2 and 4.
Explanation
★The contradictory pair is some mammals are vertebrates and no mammals are vertebrates, so the answer is 2 and 4.
★Contradictories cannot both be true and cannot both be false.
★Some mammals are vertebrates is the particular affirmative, type I.
★No mammals are vertebrates is the universal negative, type E.
★Type I and type E are exact contradictories of each other.
★The A and O pair would also contradict, but the option given here is the I and E pair, that is 2 and 4.
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