Whose pen is this 和Whose is this pen的区别在哪里

提问在句子中的成分不一样,Whose pen is this?对定语这一成分进行提问,回答是It is my pen.
Whose is this pen?对做表语的所有格进行提问,回答是This pen is mine.
看它们各自的回答就一目了然了