which of the following is/are a tautology

1992

Answer: B. a ∧ b → b ∨ c

1. A.

   a ∨ b → b ∧ c

2. B.

   a ∧ b → b ∨ c

3. C.

   a ∨ b → (b → c)

4. D.

   a → b → (b → c)

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Correct answer: B

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