UGC NET Questions (Paper – 1)

Venn diagrams use overlapping regions, typically circles, to show how different classes or sets relate to one another. By shading or marking areas of these diagrams according to the premises, one can visually check whether a proposed conclusion is forced. This method is standard in examining the validity of categorical syllogisms. Therefore the diagrams described in the stem are called Venn diagrams.

Option A:
Option A, flow charts, represent sequential steps, decisions and processes, often in computer science or management contexts. They are not designed to depict class inclusion and exclusion in the way needed for syllogistic reasoning.

Option B:
Option B, decision trees, model branching choices and outcomes, particularly in decision analysis and probability. While they can involve logical structure, they do not primarily illustrate class relationships among terms.

Option C:
Option C is correct because Venn diagrams were specifically developed to handle set-theoretic relationships, which align neatly with categorical propositions. Their overlapping circles allow us to see intersections, unions and complements, making them ideal for testing syllogisms.

Option D:
Option D, matrices, can organise numerical or logical information, but they are not the conventional visual tool for representing class inclusion patterns in introductory logic.

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.

Venn diagrams use overlapping circles to depict the relationships between classes such as inclusion, exclusion and intersection. In testing syllogisms, they visually show whether the logical requirements of the premises allow the conclusion. This graphical method provides an intuitive way to evaluate validity. Hence the diagrams mentioned in the stem are called Venn diagrams.

Option A:
Option A, flow charts, represent sequences of steps or decisions in procedures rather than set relationships in logic. They are used more in computer science and process modelling than in categorical reasoning. Thus flow charts are not the correct answer.

Option B:
Option B is correct because Venn diagrams are specifically designed to portray the logical structure of categorical propositions. By shading or marking regions, we can see how premises constrain possible cases and assess whether the conclusion follows. This matches the description provided.

Option C:
Option C, decision trees, represent branching choices and consequences and are often used in decision analysis, not in standard testing of syllogistic relations between classes. Therefore decision trees do not fit the stem.

Option D:
Option D, network graphs, depict nodes and connections for relationships like communication or social ties. They are not the conventional tool for illustrating class inclusion in traditional logic. Hence network graphs are not appropriate here.