blue moon

例句：

1. 1.The blue moon is a rare and beautiful sight.
   蓝月亮是一种罕见而美丽的景色。
2. 2. She spent the night under the blue moon.
   她在蓝月亮下度过了一个夜晚。
3. 3. The blue moon was a symbol of hope and renewal.
   蓝月亮象征着希望和重生。