Have you seen __ umbrella here?--You mean __ black one .It was here a moment ago
a ,a
你看见一把雨伞吗在这儿吗?用a 没有疑问.
you mean a black one.It was here a moment ago .你的意思是 一把黑色的雨伞?它刚在在这儿.所以用a
但是也可以这样理解：you mean the black one.It was here a monent ago 你的意思是那把黑色的雨伞吗?它刚才在这儿.也就是应该用the .
到底用哪个呢?