A.50% B.60% C.80% D.70% E.90%
A.1~2mm B.3~3.5mm C.2.5~3mm D.2~2.5mm E.3.5~4mm
A.牙骨質(zhì) B.牙本質(zhì) C.牙釉質(zhì) D.長骨骨干 E.以上都不對