dont的過去式是什么

　　例句：

　　I know him, but we dont frequently see each other.

　　我認識他，但我倆并不常來常往。

　　Dont' think it will all be that easy.

　　不要把這事看得那么容易。

　　Don't speak in a loud voice!; Dont't make noise!

　　不要大聲喧嘩！

　　B: I dont think it fun to travel in big cities.

　　B：我認為在大城市旅行不好玩。