Which of the following options represents an equivalence formula in modal logic?

Group of answer choices

$\backslash$geoquad $($P $->$ Q$)($P $->$ Q$)$

$\backslash$geoquad P $$P

$($P $$ Q$)$P $$Q

$\backslash$geoquad $($P $->$ Q$)\backslash$geoquad P $->\backslash$geoquad Q