窝洞的洞深一般为

窝洞的洞深一般为
A.在釉牙本质界下0.2-0.5mm
B.在釉牙本质界下0.5-0.7mm
C.在釉牙本质界上0.2-0.5mm
D.在釉牙本质界上0.1-0.2mm
正确答案：在釉牙本质界下0.2-0.5mm