成釉器可以形成( )
A．牙周膜B．牙骨质C．牙槽骨D．牙釉质E．牙本质
参考答案：D
0.5m3的冰块完全融化为水后，体积变为0.45m3，则冰块的质量是 ______kg，冰块的密度是 ______g/cm3．
— Mary didn't come to school, did she?
— _____ She was ill in bed.[ ]
A. No, she did.
B. Yes, she did.
C. No, she didn't.
D. Yes, she didn't
