A.有人監(jiān)護(hù); B.在污水池區(qū)域設(shè)置救生圈; C.穿救生衣; D.套戴救生圈;
A.皮革; B.化纖; C.橡膠; D.棉花;
A.800mg/L; B.1200mg/L; C.1400mg/L; D.1600mg/L;