Do you know where the post office is?为什么要加个is,去掉不是也行吗

补充:Do you know where... Where is home?Do you know? Do you know where is my angel? Do you know where it is ?是什么意思 Do you know where sugar is （? ） do you know where the sahara D______is Do you know where sugar is 什么? do you know where suger is p--- Do you know where the meeting Do you know where is inner mongolia? DO you know where he lives?对 还是DO you know where does he live?对 do you know where her home is还是do you know where is her home do you know where is the washroom?还是do you know where the washroom is? do you know where it is 为什么不是do you know where is it? do you know where shop is和do you know where the shop is哪个对? Do you know where West Late is?还是Do you know where is West Late?谢谢 DO YOU KNOW什么情况下后面加疑问语序?Do you know-------------?a.who will clean th classroom b.how long will ther stay herec.what did he say d.where he has gone 求do you know where you're going to英文歌词