在非线性元件的伏安特性研究中，物质按导电性能可分为（）
A.半导体和导体
B.导体和绝缘体
C.绝缘体和半导体
D.导体、半导体和绝缘体
参考答案：D
某患者变色牙，要求烤瓷冠修复，对1牙体预备的要求正确的是（）
A.肩台宽度0.5mm
B.可设计为金属颈圈
C.轴面聚合度不超过10°
D.设计为龈上肩台
E.牙体颈缘预备成135°凹面肩台
用括号里所给词的正确形式填空。
1. Maria (tell) Mlke that Li Lei would get on well with others.
2. In English, he is better at (read) than (listen).
3. It seemed that they (live)a hard life.
4. He told me a piece of (disappoint) news that we didn't pass the exam.
5. He didn't know what was (happen) outside.
变色牙，要求烤瓷冠修复，对1牙体预备的要求正确的是（）