Tautology contradiction contingency – UGC NET Question

Statements A, B and C correctly define tautology, contradiction and contingency by looking at truth across all valuations. Statement E is also true because the negation of a formula that is always true must be false on every valuation, hence a contradiction. Statement D is impossible in classical logic, since no statement can be both always true and always false at once. Therefore, the complete set of correct statements is A, B, C and E only, which matches option C.

Option A:
Option A is incomplete because it omits E and therefore fails to mention the important relationship between tautologies and contradictions via negation. It lists correct information but not the full set of true statements for this question.

Option B:
Option B is incorrect since it leaves out B and includes only A, C and E, ignoring the explicit definition of contradiction that is central to the topic. Without B the description of the three categories is not complete.

Option C:
Option C is correct as it brings together the accurate definitions of the three types of statements and the fact that the negation of a tautology is a contradiction, while excluding D, which suggests an incoherent situation in classical logic.

Option D:
Option D is wrong because it includes D, which falsely claims that a statement can be both tautology and contradiction and calls that “contingent”, and it omits A, so it both accepts a logical impossibility and loses a key correct statement.