请问哪三大铜亭并称为中国三大铜亭？
参考答案：
泰山岱庙铜亭，北京颐和园铜亭，昆明鸣凤山铜亭。
使用胎头吸引术助产时，全部牵引时间不宜超过多少分钟（）。
A.10
B.15
C.20
D.25
E.30
Human facial expressions differ from those of animals in the degree __________ they can be controlled on purpose.
A．with which
B．to which
C．of which
D．for which
