The logically equivalent preposition of $p \Leftrightarrow q$ is\\ (1) $(p \Rightarrow q) \wedge (q \Rightarrow p)$\\ (2) $p \wedge q$\\ (3) $(p \wedge q) \vee (q \neq p)$\\ (4) $(p \wedge q) \Rightarrow (q \vee p)$