不及物动词+介词+宾语（名词,代词,动词ing形式）
所以介词后面是可以加代词的.宾语必在介词后.
比如：write to me ,wait for you,search for it.care about her
.
至于look it up.这里的up不是介词,而是副词.在动词加副词结构中,若是代词通常要放在中间.若是名词则随意.
比如：look up the new word ,look the new word up,look it up
cut the head off,cut off the head,cut it off