重点讲解：
1. at once 同时；一起；
例句：The teacher asked the pupils not to speak at once.
老师叫学生们不要同时说话%;|h7XmBY%wgD)@;.。
2. differentiate from 使有差别；使不同；
例句：I can't differentiate one variety from another.
我无法将这几个品种区别开来D1^LHzd0rS3Av*ys5E。
3. take advantage of 利用；占……的便宜；
例句：It never occurred to me to take advantage of him.
我决没有想到过要占他的便宜r=%br1Pg#M。
4. in turn 继而；转而；反过来；
例句：That, in turn, would be useful in reconfigurable circuits.
反过来,通过改变电路也一样有作用I7guSX#^&bE)。