问题补充：
—Do you know the girl is standing the tree?
— Yes, she is my friend, Zhang Ying.
A. that, in the front of
B. whom , under
C. who, in front of
D. which, behind
答案：
A. that, in the front of
B. whom , under
(答案→)C. who, in front of
D. which, behind
解析：句意：你认识那个站在树前面的女孩吗？是的，她是我的朋友，张英。in the front of在....的前面（内部），in front of在……的前面（外部），under在……下，behind在……后；定语从句中who/whom/that指代人，that/which指代物，who做主语和宾语，whom做宾语；先行词the girl，在定语从句中做主语，引导词国who或that,女孩站在树的外部的前面，故选C.
