动词+副词组成的词组, 如果宾语是代词, 必须放中间, pick it up；宾语是名词, 中间、后面都可以. pick up the pen pick the pen up常用的副词down/ up/ off /away/over...
动词+介词组成的单词, 代词放后面look at it look after it talk about itthink of/ about it