once引导的从句,用什么时态例句Once he ______to do something ,no one can hold him back.A made up his mind B makes up his mind 还有关于 once 其他的用法也给我介绍一下,我已经知道答案了，是 B makes up his mind只是不

once引导的从句,用什么时态例句Once he ______to do something ,no one can hold him back.A made up his mind B makes up his mind 还有关于 once 其他的用法也给我介绍一下,我已经知道答案了，是 B makes up his mind只是不
once引导的从句,用什么时态
例句
Once he ______to do something ,no one can hold him back.
A made up his mind B makes up his mind
还有关于 once 其他的用法也给我介绍一下,
我已经知道答案了，是 B makes up his mind
只是不知道为什么
请不知道的人不要乱答

once引导的从句,用什么时态例句Once he ______to do something ,no one can hold him back.A made up his mind B makes up his mind 还有关于 once 其他的用法也给我介绍一下,我已经知道答案了，是 B makes up his mind只是不
选B.
Once的用法
1.once用作连词时,意为“一旦……就……”,用于连接时间状语从句,相当于as soon as.如：Once you start,you will never give up.一旦你开始了,你就不要放弃.
Once you begin to read it,you will like it.一旦你开始读,你就会喜欢它.
Physics is easy to learn once you understand the rules.一旦你理解了规则,物理就不难学了.注意：once引导的是时间状语从句,从句要用一般现在时代替将来时.
2.once用作副词时,意为“曾经；一度；从前”.它是一个不确定的时间副词,其位置一般是在行为动词之前,系动词之后.
如：Once he lived in America,but now he lives in England.
他曾经生活在美国,但现在他生活在英国.
His song was once very popular among the young people.他的歌一度在年轻人中很流行.
My father once employed a young man named Johnson.
我的父亲曾经雇佣了一个名叫约翰逊的小伙子.
3.once用作副词,也可意为“一次”的意思.两次是“twice”,三次是“three times”,四次是“four times”.The old professor comes to see us once a week.那个老教授一周来看我们一次.Tell us the story once more.把故事再给我们讲一次.
4.注意once用作副词时,在句中的位置不同表示的意思也不同,所以要特别注意.如：
I once went to Shanghai.我曾经去过上海.I went to Shanghai once.我去过上海一次.
5.once构成的一些短语的用法：
（1）at once（立刻；马上）
All of you should go there at once.你们所有人都应该立刻去那儿.
Finish the task at once.请立刻完成任务.
（2）once again（再一次；又一次）,相当于once more.
Let me hear you sing once again/ once more.让我听你再唱一遍吧.
Read the passage once more.把课文再读一遍.
（3）once in a while（偶尔；间或）
We went to see our English teacher once in a while.我们偶尔去看我们的英语老师.
（4）all at once（突然）,相当于suddenly.
All at once,they rushed out altogether.突然,他们都一起冲出去了.
（5）once upon a time（很早以前；从前）
Once upon a time there was an old man named John Hill.从前有一个名叫约翰·希尔的老人.

made up his mind
用虚拟语气 所以用过去式