发育性髋关节脱位的病理改变主要发生在（）
A.髋部的肌肉、韧带
B.髋臼、股骨头、颈和关节囊
C.髋部的神经、血管
D.骨盆
E.脊柱
参考答案：B
When I try to find _______ that prevents so many people from taking part in the program,it seems to me that there are two main causes.
A．why it does
B．what it does
C．what it is
D．why it is
单层衬砌
