1 . 前
...ers negotiate(协商, 谈判) their fares (车票费用)with __6__ before(在…之前) they take a ride/(乘车).
2 . 之前
...ago/last以前/最后before之前指示代词.
3 . 以前
... when(当…时), while(当…时), as (当…时),as soon as (一…就), before(在…以前), after(在…以后), since(自…以来), till(直到…), until(直到…).
4 . 面前
The long night is beforeme , and I am tired., 在我面前的是漫漫的长夜 , 我疲倦了.