Jessica在北京学中文，她的中国朋友要是遇到了不知道用美语怎么说的词，就会来请教她。今天是方方要问的：保质期。
FF: Jessica, 你过来帮我看看，这个牛奶是不是过期了呀?
Jessica: Let me see...Hmm, I'm not sure. When did you get this?
FF: 两周前吧! 那时候牛奶大减价，我就一口气买了4瓶! 贪便宜, 可是忘了看保质期...
Jessica: Milk normally has a shelf life of a week. Shelf is spelled s-h-e-l-f, 是货架的意思。shelf life 能够放在货架上的日子，也就是保质期!
FF: 原来是这样! 那我都买两个礼拜了，我看这牛奶肯定过期了....
Jessica: I bet you're right. I think this milk is past-date. You'd better throw it away!
FF: Past-date, 这里的date就是盒子上标识的生产日期。past-date 也就是过期了的意思! 真可惜，这可是最好的牛奶，这些牛都是只吃鲜草，听古典音乐长大的!
Jessica: That sounds like a top shelf product to me! 高档商品!
FF: Top shelf, 在货架上最高的地方，就是指高档货! 那相对来说，价格便宜的产品又要怎么说呢?
Jessica: It's the opposite of that. We call it a bottom shelf product. Basically less expensive stuff is put on the bottom shelf.
FF:Top shelf product, 高档货，bottom shelf product, 便宜货! 我记住了。
Jessica: 好！那你说说看，What have you learned today?
FF: 今天我们学到的内容包括:
第一，保质期是shelf life;
第二，过了保质期可以用 past-date;
第三，高级货叫做top shelf product, 便宜货叫做bottom shelf product!