1.how soon 對(duì)（從即時(shí)起）到將來某個(gè)時(shí)刻間的時(shí)間長短提問,回答通常為 in+一段時(shí)間.如：
-How soon will you be back?
-In two days.
2.how long 對(duì)從某個(gè)時(shí)刻都另一時(shí)刻（各時(shí)態(tài)皆可）間的時(shí)間長短提問,但后跟的謂語動(dòng)詞必須為延續(xù)性動(dòng)詞,回答為 for+一段時(shí)間.也用作對(duì)長短提問.如：
-How long did he be away?(leave為短暫性動(dòng)詞,故換為短語be away)
-For ten years.
3.How often 對(duì)某個(gè)時(shí)段內(nèi)謂語動(dòng)詞發(fā)生的頻率提問,答語為 次數(shù)+一段時(shí)間（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.