https://online2.tingclass.net/lesson/shi0529/0009/9907/231.mp3
https://image.tingclass.net/statics/js/2012
講解文本：
once in a blue moon 千載難逢，極其偶爾
Mary lives far away, we only see each other once in a blue moon.
Mary住的很遠(yuǎn)，我們很難見一次。
This kind of chance comes once in a blue moon.
這種機(jī)會可是千載難逢!
瘋狂練習(xí)吧!
