a long time ago后面一定要用过去式么?

a long time ago后面一定要用过去式么? long time ago 前面一定要加 a 也就是一定是 a long time ago A long time ago A Long Time Ago 歌词 A long long time ago 歌词 a long time ago 、long long ago、once和once upon a time的区别 a long time ago 的同义词 i stopped a long time ago. a long time ago 的过去时 Not that long ago.请问这里的ago是什么意思?上句是：That was a long time ago. long long ago=Once upon a time吗? Long Time Ago 歌词 A long time ago 与 Long time agoLong time ago前必须加a吗?在句子中只用long time ago,不加a,符合语法吗? long ago 和 a long time ago 有没有区别在语法上面? there was a farmer a long time ago 否定句 a long time ago,there was a queen.翻译 on,a,the,time,lived,long,Dinosaurs,Earth,ago. This story ____a long time ago A.happened B.happen