重点讲解：
1. up and down
上上下下；来来回回；
eg. I strolled up and down thoughtfully before calling a taxi.
我踱来踱去仔细思量后叫了一辆出租车。
eg. He jigged up and down with excitement.
他激动得又蹦又跳。
2. come upon
偶然碰到（或发现）；
eg. I came upon an irresistible item at a yard sale.
在一次庭院拍卖会上，我偶然发现了一个忍不住想买的东西。
eg. I may come upon something that'll throw some extra light on this.
说不定我会发现什么新线索，把这件案子的眉目弄得更清楚些。
3. be finished with
完成；不再做（…）的；（同…）不再打交道的；（对…）不再感兴趣的；
eg. One suspects he will be finished with boxing.
人们猜想他不会再打拳了。
eg. And now you are finished with the exciting and demanding years of college ready to start on a fine career.
但是现在，你已经结束了令人激动的和需要付出努力的大学岁月，准备要开始一个美好的生涯了。