骨质疏松患者发生骨折的最常见的部位（）
A.椎体
B.髋
C.前臂远端
D.骨盆
E.肱骨
参考答案：A
My sister is three years ______than I. She is _______young _____go to school.
A．young; too; to
B．younger; enough; to
C．younger; too ;to
D．young; so; that
我国的国家标准有效期一般为（）年。
A.3
B.4
C.5
D.10
