单项选择题
A.0.01%B.0.02%C.0.03%D.0.04%
A.1x 10-4B.2x 10-4C.3x 10-4D.4x 10-4
A.10x 10-4%B.15x 10-4%C.20x 10-4%D.25x 10-4%