Necessary truth and tautology – UGC NET Question

Statements A, B, D and E are correct, while C is false. A tautology is true under every valuation and a contradiction is false under every valuation. A contingent statement is true in some valuations and false in others, so C is incorrect. If a conclusion is a tautology, there is no possible case where premises are true and the conclusion is false, so the argument is valid regardless of premises (though it may be uninformative). Distinguishing these notions helps in validity checking in UGC NET, so E is also correct.

Option A:
Option A is incorrect because it omits D. Since D is true in classical logic, A, B, E only is incomplete.

Option B:
Option B is correct because it includes exactly the true statements A, B, D and E and excludes C, which misdefines contingency.

Option C:
Option C is wrong because it includes C, the false claim that a contingent statement is true in all valuations.

Option D:
Option D is wrong because it includes C (false) and omits B (true), so A, C, D, E only cannot be correct.