How long表示 “時(shí)間多久或物體多長(zhǎng)”， 表示時(shí)間側(cè)重指 “一段時(shí)間”。針對(duì) “How long” 的回答一般是時(shí)間段，如 “for three days”, “three years” 。
例如: -How long were you away last year?
-About two weeks.

How soon表示 “多久之后”，主要用來對(duì)表示將來的一段時(shí)間提問。How soon的回答一般是:“ in + 時(shí)間段”，如 “ in two days” “in five years”。
例如: -How soon will you be ready?
-I’ll be ready in five minutes.