The principal has decided -----the prize winner will be.A.who B.whom 答案解析：所填之空缺表语成分,填whoThe principal has decided 【who】the prize winner will be.A.who B.whom 校长决定了获奖者将是谁.句...作表语的时候只能用主格吗？一般情况 ，如果是疑问代词，做主语或者做宾语都用WHO ,一般情况下，如果做人称代词，口语中多用宾格代词代替主格代词做表语