1.how soon 对（从即时起）到将来某个时刻间的时间长短提问，回答通常为 in+一段时间。如：
-How soon will you be back？
-In two days.
2.how long 对从某个时刻都另一时刻（各时态皆可）间的时间长短提问，但后跟的谓语动词必须为延续性动词，回答为 for+一段时间。也用作对长短提问。如：
-How long did he be away?(leave为短暂性动词，故换为短语be away)
-For ten years.
3.How often 对某个时段内谓语动词发生的频率提问，答语为 次数+一段时间（once a day, three times a week等）,也可用never、seldom等回答。如：
-How often does he visit his grandpa?
-Twice a month.
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。
练习题
How soon will you leave for Beijing?
In a week.
How long do you stay at home every week?
For two days.
How often do you go home?
Once a week./ Once a month.
How often do you watch TV?你多久看一次电视？
Once a week.一星期一次
How often do you swim? 你多久游戏一次？
How many times did you swim?
I go to see my parents once a month.(就once a month 提问）--How often do you go to see your parents?
I have been to Shanghai three times.(就three times提问）--How many times have you been to Shanghai?
how often 就频率提问
how often意为“多久……次、是否经常”，用来提问在某一特定的时间进行某个动作的次数，答语通常是always，usually，often，sometimes，once/twice a day/month等。
—How often do you get to school very early? 你多久早到校一次？
—Usually. 通常。
—How often do you see a film? 你多久看一次电影？
—Once a month. 每月一次。
How often: 是对频率的提问
例如：how often does he purchase ?
他多久采购一次？
how many times :就是对次数进行提问：
如：how many times did he purchase in this year?
今年他采购了几次？
How many times do you go to the park in a month?
How many times就次数提问
how often 就频率提问
how often意为“多久……次、是否经常”，用来提问在某一特定的时间进行某个动作的次数，答语通常是always，usually，often，sometimes，once/twice a day/month等。
—How often do you get to school very early? 你多久早到校一次？
—Usually. 通常。
—How often do you see a film? 你多久看一次电影？
—Once a month. 每月一次。
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其他知识点
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。例如：
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？
how far问的是有多远，可以用以下几种方法回答
①It's ＋ 一段时间's +走一类的动词
②It's+距离
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