单项选择题
A.3~4minB.4~6minC.5~7minD.6~8minE.8~10min
A.0.4mmB.0.6mmC.0.8mmD.1.0mmE.1.5mm
A.金属基底冠表面清洁B.预热较慢C.瓷与合金膨胀系数不匹配D.瓷粉致密E.烧烤温度较低