重点讲解：
1. pick up the tab (替一群人)付账，承担费用；
Pollard picked up the tab for dinner that night.
那天的晚饭是波拉德掏的钱B7.ivZs1qm8;Qdu&fv。
2. trade sth. for sth. 用…进行交换；互相交换；
Tom made me an offer I couldn't refuse. He asked me to trade his computer for my old cell phone. He must be crazy!
汤姆给我提供了一个我难以拒绝的条件，他要我用我的旧手机交换他的电脑JTDCg%lNK|~q。他一定是疯了！
3. watch out for 密切注意；戒备；提防；
He called out to them to watch out for the unexploded mine.
他冲他们大喊，叫他们小心哑雷]yRk1wYhJ]rETAT。
4. in effect 其实；实际上；
In effect, the two systems are identical.
实际上，这两种系统完全一样p7P#.9^(XZCHP。