once in a blue moon 为什么 解释为 机会难得,绝无仅有?

once in a blue moon 为什么 解释为 机会难得,绝无仅有? Once In A Blue Moon 歌词 请问 once in blue moon This is a chance once in a blue moon, Once in a blue moon 这句话话是啥意思啊 "I haven't seen her once in a blue moon. once in a blue moon 出处是哪里? 求魂音泉的once in a blue moon的罗马音 You only get a chance like this once in a blue moon.这句话要怎么解释 once in a blue moon 意思和once in a while一样嘛? it happend once in the blue moon there is once in blue moon i havetogotowork,it's a blue Mond