You should say "Thank you"when someone passes you the salt on the table,when someone walking beforeyou keep the door open for you,when someone says you have done your work well,you have bought a nice thing,or your city is very beautiful.（1~2）1.为什么when someone says 中用says而不用saying,况且上文也有when someone walking before you keep the door open for you（难道是句中的before 可是都是介词后的动词加ing呀）2.为什么when someone walking before you keep the door open for you中要用keep而不用keeping
问题描述：
You should say "Thank you"when someone passes you the salt on the table,when someone walking before
you keep the door open for you,when someone says you have done your work well,you have bought a nice thing,or your city is very beautiful.（1~2）
1.为什么when someone says 中用says而不用saying,况且上文也有when someone walking before you keep the door open for you
（难道是句中的before 可是都是介词后的动词加ing呀）
2.为什么when someone walking before you keep the door open for you中要用keep而不用keeping,句子中不是有before吗
3.Have your parents flown to Shanghai?
Yes.They went there to see the fashion show.
问句中为什么用现在完成时,答句中用过去时.
答
1.句中的时态是一般现在时,when引导时间状语从句,在时间状语从句中将来时态都要用现在时代替；2.when someone walking before you 中”walking before you“是修饰someone的,意思是“走在你前面的人”,强调状态,所以...