—Do you know the girl _____is standing under the tree? —She is my little sister.

--Do you know the girl ________ is standing under the tree?

--She is my little sister.

1. A.
   who
2. B.
   whom
3. C.
   whose
4. D.
   which

--Do you know the girl        is standing under the tree?

--She is my little sister．

A．who                    B．whom                  C．whose                   D．which