标志层是地层中（）、（）、（）、容易识别的岩层或矿层。
参考答案：厚度不大；岩性稳定；特征明显
Sandy's never willing to change any of her opinions.It's no use with her. [ ]
A.having argued
B.argued
C.arguing
D.to argue
磁性矫顽力
