重点讲解：
1. up front
预付地；先期支付地；
eg. Some companies charge a fee up front, but we don't think that's right.
有些公司预先收费，但我们认为那是不对的。
eg. You usually have to pay three months rent up front.
通常你需要提前支付3个月的租金。
2. plenty of
（尤指足够的或超出需要的）丰富，充足，大量；
eg. Foreign investors see plenty of opportunities.
外国投资者看到了大量的机会。
eg. She is in the fortunate position of having plenty of choice.
好在她有很多选择。
3. stay on
（在别人都已离开或自己打算离开的时间后）继续留下；
eg. She will stay on until a replacement is found, and then return to research at stanford.
但是她会留下来直至找到合适的代替者，然后她将回到斯坦福的研究工作中。
eg. I'm not sure whether to resign or stay on.
我拿不准主意是辞职还是留任。