(2) Sand can isolate combustible substances from oxygen, so as to achieve the purpose of fire fighting, so fill in: isolate air or oxygen;
(3) It is forbidden to carry inflammable and explosive articles on the bus, because firecrackers and alcohol are inflammable and explosive articles. Therefore, fill in: ad;
(4) The bus should be equipped with fire-fighting equipment that meets safety measures. B Bus seats are made of flame retardant materials, which is a safety measure. C it is a safety problem to train drivers and passengers on fire safety knowledge, and all three methods are reasonable. Therefore, fill in ABC. ..
So the answer is: (1) low; (2) Isolated from air or oxygen; (3)AD; (4)ABC。