p ↔ q = (p→ q) ∧ (q→p)
=(¬p∨q) ∧ (q→p) --------option(B)
=(¬p ∨ q) ∧ (¬q ∨ p) = (¬p ∨ q) ∧ ( p ∨ ¬q)------------option(A)
= (¬p ∧ p ) ∨ (¬p ∧ ¬q ) ∨ (q ∧ p ) ∨ (q ∧ ¬q ) (Distributive law)
= (¬p ∧ ¬q ) ∨ (q ∧ p ) = (¬p ∧ ¬q ) ∨ (p ∧ q )----------option(D) ((¬p ∧ p )=0,(q ∧ ¬q )=0)