单项选择题
A.0℃ B.-5℃ C.-55.2℃ D.-87.4℃
A.0℃ B.3.6℃ C.10℃ D.15℃
A.5ppm B.10ppm C.20ppm D.40ppm
A.1ppm B.5ppm左右 C.50ppm左右
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