Do sit down是怎么回事为什么前面还有个DO啊,是助动词吗,为什么要加呢?在口语里显的礼貌吗

Do sit down是怎么回事为什么前面还有个DO啊,是助动词吗,为什么要加呢?在口语里显的礼貌吗 Do sit down,want you?为什么用want you? sit down to do可以吗 “Sit down.”said the teacher.为什么动词在主语前?是倒装句么? I'm tired.Why do you sit down?怎么改 Do sit down的反意疑问句是什么 come here and sit down,为什么不用come here and to sit down 为什么不可以说sit down by the table?为什么不是sit down by the table,而是sit down at the table? sit on 和sit down的区别please give me a bench ()A.to sit down B.to sit on为什么选B 不选A 非谓语句子there is noting ( A )but ( )down and wait for him ( ) back.A to do sit to come B to do sit come C to do to sit to come D to be done to sit coming 为什么只能用A? 为什么sit后有时候加down有时候加on This chair is comfortable --------( )A.to sit B.to seat C.to sit on D.sit down 为什么选C class sit down Sit down,please. sit down怎么读 英语Sit down,please, sit down的意思 Sit down,piease.