As we know, paper is made         wood, wood is made            paper.[ ]

A. of; from                        

B. from; into    

C.into; by                          

D. in; from

探测站机房需坦设设备地线和防雷地线各一条，两条地线相距（），接地电阻小于10欧姆，接地装置不得与电力系统重复接地，建筑物避雷针接地等相距20米。