how long,how often,how soon三者都可以譯成“多久”.how long用來提問“多長(zhǎng)時(shí)間”,對(duì)“一段時(shí)間的長(zhǎng)短”提問時(shí)用,與延續(xù)性動(dòng)詞連用；how often用來提問某動(dòng)作或狀態(tài)發(fā)生的頻率,對(duì)“一段時(shí)間內(nèi)發(fā)生了幾次活動(dòng)”（always,usually,often,never或twice a day等表示頻度的詞或短語）提問時(shí)用；how soon用來提問某人要“多快”能做好某事,或某事要“多快”能完成,對(duì)“過多少時(shí)間（就能……）”（in短語）提問時(shí)用,常用于將來時(shí).而how far意思是“多遠(yuǎn)”,對(duì)距離提問時(shí)用.
eg:
How long did you stay there?
你在那兒呆多久?
How often do his parents let him watch TV?
他父母多久讓他看一次電視?
How soon will her husband come?
她丈夫多久會(huì)回來?