我国合同鉴证制度实行的是( )原则。
A．自愿鉴证
B．不必鉴证
C．统一鉴证
D．强制鉴证
参考答案：A
椎间盘突出的体征不包括（）。
A.椎旁叩击征阳性
B.脊柱侧突
C.循坐骨神经行程有压痛
D.直腿抬高试验和加强试验阳性
E.下肢"4"字试验阳性
The hostess of the party, who ______ as a doctor for five years, is president of a famous private school.
A．worked
B．has worked
C．works
D．had worked
