The reason ___ he can’t come is ______ he has to work late.

A．because; that

B．that; that

C．why; that

D．why; because

在垫层上进行基础放线前，一定要先检查基坑上建筑物四廓轴线控制桩位置没有碰动后，再以控制桩为准向垫层投测“井”字定位线，作为垫层上细部施工的依据。