菌斑内的矿物质转换主要是菌斑与下列哪项之间的矿物质转换
A．牙本质
B．牙骨质
C．龈沟液
D．牙髓
E．牙釉质
参考答案：E
The school year is divided into two semesters, __________is September through December.
A．the first of which
B．the first of them
C．the first of it
D．the first of that
测井电缆的（）取决于绝缘材料的介电常数、绝缘层厚度、电缆芯数。
A.电容
B.电感
C.直流电阻
D.有效电阻
