一个英语问题：I'll sweep the floor if you (would) clean the desks and chairs.句子如题,我想知道为什么括号中要用would?if引导的从句的时态都要比主句的退后一步吗?

一个英语问题：I'll sweep the floor if you (would) clean the desks and chairs.句子如题,我想知道为什么括号中要用would?if引导的从句的时态都要比主句的退后一步吗? 阅读对话,回答下列问题（英语）mary：can you help me with the washing,tom?tom:i'm sorry,i'm busy with the robot,catherine.mary; i go shopping every day.i cook three meals every day.i wash dishes every day.i make beds every day.i sweep th If I can't sweep you off your feet ,I'll just wear you down. 英语卷I cen sweep the floor划线句子提问?(在sweep the floor下面提问) 英语缩写I'll是什么意思?I'll I can sweep the 英语I'll‘ll指什么 I’ll take it 英语 英语I,ll什么意思 I'll英语中是什么意思? N I N A N O C M 用这几个字母拼一个单词,应该是食品类的.可以装在罐头里的.有三个N，但是只有一个M 另外 GU TH LL WI NI MA LS EY OU EA ID 什么顺序可以拼成一个句子。呵呵，这是游戏里的问题，题 I (sweep) the floor now. 关于歌曲Crazy baby的歌词问题劳驾那位英语好的,帮忙把Crazy baby着首歌的英文歌词翻译 歌词如下：Crazy baby,the spirit of the motion Don’t let me feel devotion,And every day I’ll always love you Baby,so let me see th i made him sweep/swept the floor sweep 还是swept 英语问题（我会回来）I'll back or I'll be back?顺便问一下,我很快回来.怎么说? I sweep the room with my father and mother 的英语短文（50字左右） 初二英语（选择适当得句子补全对话）A:Hey,Jerry.Would you mind helping me clean my car?B:____________A:____________B:OK,I'll do the windows.A:_____________B:Say,Nancy,can I use your car later?A:____________A.And I'm going to sweep the 问一个英语问题..I l__school lunch