第1个回答 2022-09-06
一、how long的用法
how long有以下两个主要意思：
1.表示多长时间,主要用来对一段时间(如three days,four weeks 等)提问.如：
A：How long did he stay here?他在这儿呆了多久?
B：About two weeks.大约两个星期.
A：How long does it take to get to London from here?从这里到伦敦要多长时间?
B：At least ten hours.至少要10个小时.
2.表示某东西有多长.如：
A：How long is the river?这条河有多长?
B：About 500 km.大约500千米.
二、how often的用法
how often 指每隔多久,主要用来对频度副词或状语(如：once a week,three times a month 等)提问.如：
A：How often does he come here?他(每隔)多久来一次?
B：Once a month.每月一次.
A：How often do you visit your mother?你多长时间看你妈妈一次?
B：Once a week.一周一次.三.whenwhen表示“什么时候,何时”的意思,副词 ad.
1.(用作疑问副词)什么时候,何时
I'd like to know when they'll let him out.
我想知道他们什么时候放他.
When did you last see Margaret?
你上一次见到玛格丽特是什么时候?2.(用作关系副词,引导关系从句)当...时
There were times when I didn't know what to do.
有些时候我不知道该怎么办才好.
连接词 conj.
1.当...时
John got engaged to her when travelling last winter.
去年冬天旅行时,约翰与她订了婚.
Don't get excited when you talk.
你说话时别激动.2.既然,考虑到
How can he get the promotion when his boss dislikes him?
既然上司不喜欢他,那他怎么会获得提升呢?3.虽然,然而
I had only fifteen dollars on me when the book I wanted cost twenty.
我身上只带了十五元钱,可是我想买的那本书定价二十元.4.在那时,然后
代词 pron.
1.什么时候,那时
Since when has she taught here?
她从什么时候开始在这儿教书的?