“折叠刀”用英语怎么说？

而且我们在他背包里发现了一把折叠刀.Andwe found a folding knife in his back pocket.那里还卖瑞士军用折叠刀,二十美元.They had a Swiss Army knife for $ 20.我花十美元买了一把非常好的折叠刀.I got a really good pocketknife for $ 10....