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

Group of answer choices

$\backslash$geoquad $\backslash$geoquad P $\backslash$geoquad P

$($P $->$ Q$)$P $->$Q

$$P $$P

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