英語中的問句一個(gè)重要標(biāo)志是倒裝,即：把be（可變形為am、is、are、was、were）動(dòng)詞或情態(tài)動(dòng)詞（如：can、may、must、should等）置于主語前,如：He is a doctor.（他是醫(yī)生.）→Is he a doctor?（他是醫(yī)生嗎?）She is at home.（她在家里.）→Where is she?（她在哪兒?）.如果既無be動(dòng)詞有無情態(tài)動(dòng)詞,則需用助動(dòng)詞do置于主語前來構(gòu)成問句,如：They exercise three times a week.（他們一周鍛煉3次.）→How often do they exercise?（他們一周鍛煉幾次?）本句中的do即同此理.