JEE Main · 2020 · 08 Jan 2020 · Shift 2 · Mathematical Reasoning *

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Which of the following statement is a tautology?
  1. (A)
  2. (B)✓ Correct
  3. (C)
  4. (D)

Answer: (B)

Solution

Simplify by De Morgan's law to , so the statement becomes . Whenever the antecedent is true, is true, which makes true; and whenever the antecedent is false the implication is automatically true. Being true in every case, the statement is a tautology.

JEE Main · 2020 · 08 Jan 2020 · Shift 2 · Single correct option

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