UGC NET Questions (Paper – 1)

Only statement D is wrong; all the others correctly describe valid immediate inferences. It is true that E and I propositions are simply convertible and that obversion preserves logical equivalence for the standard forms. From “All S are P” we cannot with certainty derive “Some P are S”, and UGC NET questions frequently ask which of these inferences are valid. However, from “Some S are not P” we cannot infer “No S are P”, since the particular negative does not entail the universal negative, making D the sole incorrect statement.

Option A:
Option A is correct because it isolates D as the only false statement and leaves A, B, C and E untouched as valid logical claims. It accurately reflects standard rules for conversion and obversion and the limits of what can be inferred from an O-proposition. This matches both logic texts and exam-style reasoning.

Option B:
Option B is incorrect since it treats A as wrong along with D, even though A correctly states that the converse of an A-proposition does not follow with certainty. Including A among the wrong statements therefore misrepresents a genuine logical restriction.

Option C:
Option C is wrong because it adds C to the set of allegedly wrong statements. C is in fact correct, as obversion yields a logically equivalent proposition in all four standard forms, so C and D only misclassifies an important logical law.

Option D:
Option D is also incorrect since it groups B with D, thereby wrongly branding the simple convertibility of E and I propositions as incorrect. B and D only thus fails to respect the standard conversion rules that students must know for UGC NET.