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.