how often的用法how often 什么时候对sometimes,often提问?

how long,how often,how soon三者都可以译成“多久”.how long用来提问“多长时间”,对“一段时间的长短”提问时用,与延续性动词连用；how often用来提问某动作或状态发生的频率,对“一段时间内发生了几次活动”（always,usually,often,never或twice a day等表示频度的词或短语）提问时用；how soon用来提问某人要“多快”能做好某事,或某事要“多快”能完成,对“过多少时间（就能……）”（in短语）提问时用,常用于将来时.而how far意思是“多远”,对距离提问时用.
eg:
How long did you stay there?
你在那儿呆多久?
How often do his parents let him watch TV?
他父母多久让他看一次电视?
How soon will her husband come?
她丈夫多久会回来?