第1个回答 2008-10-01
Why did you do this?
What made you do this?
Why are you doing this?
【因为不知道你需要什么时态的，所以多写了几个。如果没有特殊说明的，一般都用一般过去式】
第2个回答 2008-10-01
Why are you doing this?
Why did you do this?
What made you do this?本回答被提问者采纳
第3个回答 2008-10-01
Why are you doing that?
第4个回答 2008-10-01
why is it that you did so?
第5个回答 2008-10-01
Why would you do this???