In propositional logic P ↔ Q is equivalent to (Where ~ denotes NOT)

1. A.

   ~(P ∨ Q) ∧ ~(Q ∨ P)

2. B.

   (~P ∨ Q) ∧ (~Q ∨ P)

3. C.

   (P ∨ Q) ∧ (Q ∨ P)

4. D.

   ~(P ∨ Q) → ~(Q ∨ P)

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