Jessica在北京學中文，她的中國朋友要是遇到了不知道用美語怎麼說的詞，就會來請教她。今天是方方要問的：保質期。
FF: Jessica, 你過來幫我看看，這個牛奶是不是過期了呀?
Jessica: Let me , I'm not sure. When did you get this?
FF: 兩週前吧! 那時候牛奶大減價，我就一口氣買了4瓶! 貪便宜, 可是忘了看保質期...
Jessica: Milk normally has a shelf life of a week. Shelf is spelled s-h-e-l-f, 是貨架的意思。shelf life 能夠放在貨架上的`日子，也就是保質期!
FF: 原來是這樣! 那我都買兩個禮拜了，我看這牛奶肯定過期了....
Jessica: I bet you're right. I think this milk is past-date. You'd better throw it away!
FF: Past-date, 這裏的date就是盒子上標識的生產日期。past-date也就是過期了的意思! 真可惜，這可是最好的牛奶，這些牛都是隻吃鮮草，聽古典音樂長大的!
Jessica: That sounds like a top shelf product to me! 高檔商品!
FF: Top shelf, 在貨架上最高的地方，就是指高檔貨! 那相對來說，價格便宜的產品又要怎麼說呢?
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, 高檔貨，bottom shelf product, 便宜貨! 我記住了。
Jessica: 好！那你說說看，What have you learned today?
FF: 今天我們學到的內容包括:
第一，保質期是shelf life;
第二，過了保質期可以用 past-date;
第三，高級貨叫做top shelf product, 便宜貨叫做bottom shelf product!
