引起成人股骨头缺血坏死的常见原因为（）
A.外伤
B.皮质激素治疗
C.酒精中毒
D.减压病
E.肾移植
参考答案：A, B, C
That year his total income, with his reward ________， ________ 12, 000 yuan.
A．added to; added up to
B．added; added to
C．added up to; added
D．adds to; adds up to
分解因式：x2y-4xy+4y=______．
