A hardware store gains subscribers to its email list by asking customers to sign up at in$-$store checkout, attending local events, and having a sign$-$up form on its website. The most active subscribers are contacts at companies making commercial purchases.

Given these circumstances, which dynamic email segment would be the most ideal option for this business to identify inactive subscribers?

subscribers from the website form who haven't engaged in $20$ days

subscribers from event sign$-$ups who haven't opened the last five emails

subscribers who made an in$-$store purchase but haven't converted in $60$ days

subscribers who made an in$-$store purchase but haven't engaged in $10$ days