who，whose，which，what作主语时，通常接一个肯定动词而不是疑问动词：

　　Who pays the bills?

　　谁付帐?(肯定动词)

　　Whose/Which horse won?

　　谁的/哪匹马赢了?(肯定动词)

　　What happened?/What went wrong?

　　出了什么事?/出了什么毛病?(肯定动词，可能的回答如We missedthe train/had an accident我们误了火车/出了事故。)

　　但who，whose等后跟be+名词或人称代词时，要用疑问动词：

　　Who are you?

　　你是谁?

　　Whose is this?

　　这是谁的?

　　What is that noise?

　　那噪音是怎么回事?

　　who，whose等作动词或介词的宾语时，整句当然需要用疑问动词。