单项选择题
A.1ppm=1000ppbB.1ppm=1/100ppbC.1ppm=1/1000ppbD.1ppm=100ppb
A.3个B.5个C.4个D.6个
A.烤干B.热风或冷风吹干C.蒸干D.灼烧
A.洗涤、涂油B.比色C.装溶液D.试漏
微信扫一扫,加关注免费搜题