充填物折断是由于
A．窝洞的点线角太锐B．洞的边缘制备于深窝沟处C．银汞合金修复体厚度不够D．悬突E．垫底材料选择不当
参考答案：C
It was rather strange how the habits of his youth clung to him still. He was 72.
A．stuck to
B．turned
C．led to
D．gave way to
现场急救中，口对口人工呼吸的吹气频率较适宜的是（）
A.12~14次/分
B.14~16次/分
C.16~18次/分
D.18~20次/分
E.20~22次/分
