答案:A
上前牙PFM全冠切端预备至少
A.1.5~2.0mmB.0.35~0.5mmC.0.8~1.5mmD.1.8~2.0mmE.2.0mm以上
English is difficult________. Nobody can learn to use it in a few minutes.
A.learning
B.to be learned
C.learned
D.to learn