下列哪项不是Begg细丝弓矫治器的“组成部分”（）
A.栓钉
B.方弓丝
C.正轴簧
D.托槽
E.带环及颊面管
参考答案：B
压力为5个大气压情况下，每增加1个大气压时，水的体积只改变（）。
A.万分之0.529
B.千分之0.529
C.万分之0.527
D.千分之0.527
Which of the following characteristic of perfect competition explains why firms in perfect competition are referred to as price takers（）
A. Each firm is small relative to the total market.
B. The demand curve is horizontal for firms in perfect competition.
C. There are many independent firms.
