介绍:
1. a blue moon 千载难逢的事
Once in a blue moon, her husband brings her gift.
她丈夫居然送她了一份礼物，真是千载难逢的一件事。
2. kill time 消磨时光
He had nothing in particular to do, so he went for a walk downtown to kill time.
他没有什么特别的事要做，所以他为了消磨时间，去市区散了散步。
3. call it a day 收工
Why don't we call it a day? I'm really tired.
我们为什么不收工呢？我真的很累了。
4. against the clock 和时间赛跑
The students were racing against the clock to finish the paper before the deadline.
学生们要赶在时间截止之前努力答完试卷。
