Which one of the following is NOT equivalent to p ↔ q?

• A. (¬ p ⋁ q) ⋀ (p ⋁ ¬ q)
• B. (¬ p ⋁ q) ⋀ (q → p)
• C. (¬ p ⋀ q) ⋁ (p ⋀ ¬ q)
• D. (¬ p ⋀ ¬ q) ⋁ (p ⋀ q)