UGC NET Questions (Paper – 1)

Obversion is an immediate inference in which a categorical proposition is transformed by switching from affirmative to negative or vice versa and replacing the predicate with its complement. For example, “All S are P” becomes “No S are non-P”. This operation preserves logical equivalence for all four standard forms. Hence the result of the process described in the stem is called the obverse of the original proposition.

Option A:
Option A, conversion, involves interchanging the subject and predicate terms while keeping quantity and quality the same or appropriately modified, as in converting “No S are P” to “No P are S”. It does not require introducing the complement of the predicate.

Option B:
Option B is correct because obversion is uniquely defined by the combination of quality change and predicate complementation. It provides a reliable way of generating an equivalent statement that often clarifies the logical content.

Option C:
Option C, contraposition, is obtained by interchanging subject and predicate and negating both, which is a different transformation usually applied to conditionals and some categorical forms. It is not the simple quality change with predicate complement described in the question.

Option D:
Option D, distribution, concerns whether a term refers to all members of its class within a proposition and is not the name of any immediate inference. It does not describe the operation of forming an equivalent proposition.

Statements A, B, C, E and F are correct, while D is false. Conversion is valid for E and I forms, obversion works by changing quality and complementing the predicate, and contraposition in its full form applies to A and O in the traditional system. Obversion is valid for all four categorical forms, and exam questions can test recognition of these operations. D is wrong because simple conversion of an A proposition is not always valid; it must usually be converted to a particular form. Therefore A, B, C, E and F only is the correct combination.

Option A:
Option A is incomplete because it stops at A, B and C and leaves out E and F, which also state correct facts about obversion and exam usage. Without acknowledging that obversion is valid for all four forms and that these operations are tested, the account is partial. Hence A, B and C only cannot be accepted.

Option B:
Option B is correct because it brings together the three operations and their main properties along with their application in UGC NET questions. It rightly excludes D, which incorrectly generalises about simple conversion of A propositions. This combination fully reflects the standard treatment of immediate inferences.

Option C:
Option C is wrong since it includes D along with B, C, E and F and omits A. Accepting D means incorrectly treating simple conversion of every A as valid, and omitting A forgets the special status of E and I in conversion. This mix of error and omission makes the option unacceptable.

Option D:
Option D is incorrect because it omits B, removing the core definition of obversion, and it also drops E. Although it mentions some correct points, without B and with the absence of E it does not capture all true statements in the list. Therefore A, C, E and F only cannot be the correct answer.