Which of the following is a tautology?

(A) (a ∨ b) → (a ∨ c)
(B) (a ∧ ¬b) → ( ¬b ∧ c)
(C) ( ¬a ∧ ¬b) → ( ¬b ∨ a)
(D) (a ∧ b) → (a → b)


Answer: (D)

Explanation: We solve each one by one with the same method and only D satisfy
Let’s Solve D
(ab)’ + a’ + b
a’ + b’ + a’ + b
a’ + 1 = 1 (b + b’ =1)
Hence, it is a tautology.


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