多数关节内强直发生在哪个年龄段
A．5岁以前
B．15岁以前
C．15～20岁
D．25岁以后
E．20岁以后
参考答案：B
Representative samples ( ) taken by the inspector from the whole lot yesterday.
A．was
B．is
C．were
D．are
圆环形卡环通常包绕基牙的
A．2个面和2个轴角B．2个面和3个轴角C．3个面和2个轴角D．3个面和3个轴角E．3个面和4个轴角
