单项选择题
A.当天下班前 B.立即 C.12小时内 D.24小时内
A.脏区、净区;颜色 B.场内、场外;类型 C.脏区、净区;类型 D.场内、场外;颜色
A.5.6ppm;1h B.5.6ppm;2h C.20ppm;1h D.20ppm;2h