what was it____they were discussing at that meetingA.whatB.whoC.thatD.which

what was it____they were discussing at that meetingA.whatB.whoC.thatD.which what was what is还是what was what was your grandma? what was that? what was wrong with what was the present? what was it what was Mr smith wondered what was going What was your previous what.day.was. what was your dream? What was the article? what was 可不可以写为 what's what it was or what it will what sth was happens是什么意思what sth was happen? what was the matter是否等同于what wrong was?