A.1小時 B.2小時 C.3小時 D.4小時
A.5mg/m3(8ppm) B.10mg/m3(9ppm) C.15mg/m3(10ppm) D.20mg/m3(11ppm)
A.20mg/m2 B.30mg/m3 C.40mg/m3 D.50mg/m4