简述方铅矿物理性质。
参考答案:
铅灰色;条痕黑色;金属光泽;平行{100}三组解理完全,解理面互相垂直;硬度2~3;密度7.4~7.6;具弱导电性和良检波性。
They are talking about Rome____they had been there before. [ ]
A. even if
B. if
C. as though
D. as
商物分离的理论使物流可以完全从()中分化出来成为独立的系统。
A.生产
B.分配
C.交换
D.流通