someone____at the door while Tom was having his supper.A.was knocking B.has knocked C.is knocking D.knocked 我选的A,但老师说是错的.是否选D?若是when结果是否不同?

Just at that time,I heard someone____at the doorA.knockB.knocksC.knockedD.to knock a.We were watching TV when we heard the door____b.We were watching TV when we heard someone____at the door(knock)老师说第一个是knocked,我认为不是heard do和heard doing么?这儿听到敲门完整是动作不是用do么?加上是被动,所 While i was reading i heard someone____at the door of partiesA knocked B knocks C to knock D knock someone____at the door while Tom was having his supper.A.was knocking B.has knocked C.is knocking D.knocked 我选的A,但老师说是错的.是否选D?若是when结果是否不同? do the do the dishes是什么意思 do the chores do you play the DO you look the do the Laundry 是什么意思 do the laundry翻译? do the job do the shopping造句 let him do the do the trick for please do the right do it the hard The passwords do not