Whose pen is this? - it's mine.

这是谁的钢笔？——是我的钢笔。

Excuse me. Whose pen is this?

对不起。这是谁的钢笔？

Whose pen is this? It's mine.

这是谁的钢笔？是我的。

Whose pen is this? — It's Kate's.

这是谁的笔？是凯特的。

Whose pen is this?

这是谁的笔？

Whose pen is this? Let me see. Oh, yes, it's Mary's.

这是谁的钢笔？我来看一看，哦，是玛丽的。

Can you help me find out whose pen this is?

你能帮我查明一下这是谁的钢笔吗？

Whose is this pen?

这只钢笔是谁的？

Whose Ballpoint Pen is This?

这是谁的圆珠笔？

Whose is this pen?-It's mine.

这是谁的笔?-是我的。

She asked me whose pen this is.

她问我这是谁的钢笔。