都是一些习惯固定的用法
in 表示状态
in progress(在进行中),in a dilemma(处于进退两难的境地),in a hurry,in a tight corner(处于困难中),in action(在行动中),in an emergency,(处于紧急情况中),in anxiety,in astonishment,in bad mood(心情不好),in bad temper(心情不好,生气)等等
on 表示状态
on a diet(在节食),on a picnic,on a trip,on a vacation trip,on a visit,on a voyage,on a walk
at 表示状态
at a disadvantage(处不利地位),at a lecture,at a run(跑着),at breakfast,at call(随叫随到),at church,at dinner,at ease(悠闲自得),at feed,at gaze,at grass,at graze,(在吃草) at hand(在手边),at leisure (空闲着),at meals,at peace,at play,at rest,at school,at study,at table(在吃饭),at the bar(受到公开审问),at the meeting,at the piano,at the wheel(在驾车),at war,at work没有具体分别吗？只是一种习惯的搭配