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.牙釉质
B.牙本质
C.牙骨质
D.牙髓
E.龈沟液
参考答案：A
The Internet plays an important role in our life. Without the Internet, life ________ quite different nowadays.
A．would be
B．will be
C．is
D．was
