作业帮填入适当引导词
来源：学生作业帮 编辑：作业帮 分类：英语作业 时间：2024/05/11 20:02:24
Do not leave the room____you have finished the test.为什么填before而不可以填until和unless？请老师详细讲讲。
解题思路： before后可以接完成时，而untill只可以接过去时和现在时。
解题过程：
before作为连词时的基本意义是“在……之前”，用于表示时间或顺序。
此题应该填before，该句的意思是：在你完成考试之前你不能离开房间。before表示先后顺序。
unless与until均为从属连词,unless表“除非”,强调条件,引导条件状语从句;until表“直到”,强调时间的延续,引导时间状语从句。
1. I didn't know the news until my teacher told it to me. ( 句1动词didn't know表明该句强调时间的延续,表“我不知道这消息”的状态一直延续到“老师告诉我”,因此应用until引导时间状语从句)
2. I couldn't know the news unless my teacher told it to me.（动词couldn't know表明该句强调条件,表“我不可能知道这消息,除非老师告诉我”,因此应用unless引导条件状语从句）
3.—Was his father very strict with him when he was at school?
—Yes. He had never praised him until he became one of the top students in his grade. （表明“他爸爸从来没有表扬他”的状态 一直延续到“他变成年级最好的学生之一”,因此也应用until引导时间状语从句。）
二、作为从属连词引导的从句常用一般现在时表示将来
unless引导的条件状语从句和until引导的时间状语从句常用一般现在时表示将来。
例1:除非邀请你否则别进来。
Don't come in unless you're invited to.
例2:除非他来,我们不可能去。
Unless he comes, we won't be able to go.
最终答案：略
解题过程：
before作为连词时的基本意义是“在……之前”，用于表示时间或顺序。
此题应该填before，该句的意思是：在你完成考试之前你不能离开房间。before表示先后顺序。
unless与until均为从属连词,unless表“除非”,强调条件,引导条件状语从句;until表“直到”,强调时间的延续,引导时间状语从句。
1. I didn't know the news until my teacher told it to me. ( 句1动词didn't know表明该句强调时间的延续,表“我不知道这消息”的状态一直延续到“老师告诉我”,因此应用until引导时间状语从句)
2. I couldn't know the news unless my teacher told it to me.（动词couldn't know表明该句强调条件,表“我不可能知道这消息,除非老师告诉我”,因此应用unless引导条件状语从句）
3.—Was his father very strict with him when he was at school?
—Yes. He had never praised him until he became one of the top students in his grade. （表明“他爸爸从来没有表扬他”的状态 一直延续到“他变成年级最好的学生之一”,因此也应用until引导时间状语从句。）
二、作为从属连词引导的从句常用一般现在时表示将来
unless引导的条件状语从句和until引导的时间状语从句常用一般现在时表示将来。
例1:除非邀请你否则别进来。
Don't come in unless you're invited to.
例2:除非他来,我们不可能去。
Unless he comes, we won't be able to go.
最终答案：略