单项选择题
A.-1ppmB.零C.+1ppmD.±1ppm
A.0.01ppmB.0.1ppmC.0.5ppmD.1ppm
A.视差改正B.加常数改正C.气象改正D.乘常数改正
A.频率B.振幅C.周期D.波长
微信扫一扫,加关注免费搜题