1.natural selection 物竞天择；自然淘汰

例句:Darwin thinks that natural selection is the chief factor in the development of species.
达尔文认为自然淘汰是物种发展中的主要因素。

2.get out of 逃避；避免

例句:It's amazing what people will do to get out of paying taxes.
人们为逃税而做出的种种事情令人吃惊。

3.at a time 一次；每次

例句:Can I borrow two books at a time?
我可以一次借两本书吗？

4.make up for 弥补

例句:Her beauty can't make up for her stupidity.
她的美丽不能弥补她的愚蠢。