—Have you seen ________ pen?I left it here this morning.—Is it _________ black one?I think I saw it somewhere.A.a,the B.the,the C.the,a D.a,aA为什么不可以?

Question

—Have you seen ________ pen?I left it here this morning.
—Is it _________ black one?I think I saw it somewhere.
A.a,the B.the,the C.the,a D.a,a
A为什么不可以?

Answer 1

A和D不同的是第二个空,Is it a black one?
这里问的时候并不确定丢的那支钢笔是他所看到的黑色钢笔,所以用a来泛指,翻译成中文就是：是『一支』黑色的钢笔吗?
而不是“是『那支』黑色的钢笔吗”.