dont的过去式是什么

　　例句：

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

　　我认识他，但我俩并不常来常往。

　　Dont' think it will all be that easy.

　　不要把这事看得那么容易。

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

　　不要大声喧哗！

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

　　B：我认为在大城市旅行不好玩。