as for 至于 （答案）
as to 关于,表原因的情况较多,
eg.As to i'm a student,i need lots of working experience for applying a part time job.
as of 自从...起...截止
eg.I know that as of last week he was still unmarried.
as from 从...起 基本上和as of 是一个意思.但是这个不仅表示时间也可表示距离.