组成牙本质主要的无机物为
A．碳和磷酸钙矿物质B．铁和锌C．钙和磷D．氟和氯E．镁和钠
参考答案：A
仓库总体结构中的主体部分是装卸作业区。（）
-It's a good idea. But who's going to ________the plan?
-I think Tom and John will. [ ]
A. get on
B. get off
C. get through
D. go through
