set off on \set off for\set off doing 意义的差别

set off 是固定搭配,至于后边的借此要看句子成分.
set off 出发,动身,启程.
set sth off 引发,触发某事
偏向于动身,出发,一般不指具体做某事
具体做什么是 set about doing sth