who bought it 和 who did bought it 哪一个正确在新概念2,第10课的课后选择题,我查了很多资料,还是不明白为什么要选who bought it,

who bought it 和 who did bought it 哪一个正确在新概念2,第10课的课后选择题,我查了很多资料,还是不明白为什么要选who bought it, who bought it?和who did buy it?不是有动词该加个助动词吗.像 what did you say?..did的助动词. who bought it?和who did buy it?不是有动词该加个助动词吗.像 what did you say?..did的助动词. This is the umbrella ()last mouth.A.which I bought it B.which I boughtC.that I bought itD.who I bought It was my grandfather who bought the instrument many years ago可以写成my grandfather has bought the instrument many years 还有为什么一定要it做形式主语?直接my grandfather who bought the instrument many years ago不行吗? who Who WHO who who Who who is it和who it is哪个对?都什么意思.为什么who you are对 Quiz back:every body come here .the man who made it,doesn't want itthe man who bought it,doesn't need itthe man who needs it doesn't know itwhat is it? who is it who can do it? who did it? who can it 急要 （）is the man（）your father is talking to?A who which B who whom C whom which D whom whomCan you show me the bike（）yesterdayA that you bought it B which you bought it