什么叫自由弯曲？
参考答案：
当弯曲终了时凸模、毛坯、凹模相互吻合后不再发生冲击作用。
Your sister had a bad cold, ______ she? [ ]
A. wasn't
B. doesn't
C. hadn't
D. didn't
请从所给的四个选项中，选出最符合左边五个图形一致性规律的选项（）
A．A
B．B
C．C
D．D
