贵州省铜仁和六盘水的主要矿产是[ ]
A.铜矿和煤炭
B.汞矿和铁矿
C.汞矿和煤炭
D.铜矿和锡矿
答案:C
We might say that the earliest tools were a means of extending the human being own bodily powers.
RH-KTB法对一些关注的元素能够降到较低水平,处理后钢液中()
A、W[H]<1.5ppm
B、W[N]<30PPm
C、W[S]<50PPm
D、W[O]<30ppm
E、W[C]<20ppm